GD1.1 | Observational Geodynamics: linking Earth surface, volcanic processes and mantle dynamics since Gondwana formation
EDI
Observational Geodynamics: linking Earth surface, volcanic processes and mantle dynamics since Gondwana formation
Co-organized by GM8/GMPV10
Convener: Ingo L. Stotz | Co-conveners: Daniel O'HaraECSECS, Matthieu Kervyn, Paula CastilloECSECS, Megan HoldtECSECS, Victoria Milanez Fernandes, Sergei Lebedev
Orals
| Thu, 18 Apr, 08:30–12:30 (CEST), 14:00–15:45 (CEST)
 
Room D2
Posters on site
| Attendance Fri, 19 Apr, 10:45–12:30 (CEST) | Display Fri, 19 Apr, 08:30–12:30
 
Hall X2
Posters virtual
| Attendance Fri, 19 Apr, 14:00–15:45 (CEST) | Display Fri, 19 Apr, 08:30–18:00
 
vHall X2
Orals |
Thu, 08:30
Fri, 10:45
Fri, 14:00
The Earth's lithospheric movements and geomorphology serve as a crucial lens for understanding the dynamic behavior of the planet's interior. Surface observations offer key insights into mantle convection patterns across space and time, while seismic data provides a contemporary snapshot, and they constitute important constraints for theoretical models. Geological records contribute invaluable spatial-temporal information on the historical vertical motion of the lithosphere. Geomorphology of volcanoes and volcanic features contains inherent information on the wide range of geologic and geomorphic processes that construct and degrade them. These collective observations facilitate addressing still-standing debates, for instance on mechanisms (i.e. active margin-related versus mantle plume-related),, amalgamation/collision timings, and the evolution of biosphere pathways leading to the formation of Gondwana.

This session offers a comprehensive examination of Earth's dynamic processes since Gondwana formation, encompassing geophysical, geochemical, geomorphological, seismological, stratigraphic, and volcanic aspects, along with investigations in submarine and subglacial environments, and numerical modeling. It presents a platform for diverse presenters and attendees, spanning various disciplines, demographics, and career stages, to actively participate in addressing exciting and emerging challenges in Earth science.

Orals: Thu, 18 Apr | Room D2

Chairpersons: Paula Castillo, Victoria Milanez Fernandes, Ingo L. Stotz
Evolution of the paleo-Pacific margin of Gondwana
08:30–08:40
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EGU24-15374
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On-site presentation
Aisha Al-Suwaidi, Micha Ruhl, David Kemp, Marisa Storm, Stephen Hesselbo, Hugh Jenkyns, Tamsin Mather, Lawrence Percival, and Daniel Condon

Lower Jurassic sedimentary successions from the Neuquén Basin, Argentina are unique in the abundance of radiometrically datable material (ash-beds) present, which can be tied to bio- and chemostratigraphic (carbon-isotope) zonations. Here, we present new U-Pb radio isotopic dates, integrated with carbon-isotope and Hg/TOC data, from three localities in Argentina (Arroyo Lapa, Arroyo Serrucho/Las Overas and Chacay Melehue) to generate a biostratigraphically calibrated composite carbon-isotope curve and geochronological framework for the Pliensbachian–Toarcian transition in South America. Using a Bayesian framework we present an age-depth model for this composite record and estimate the age and duration of key intervals extending from the Latest Pliensbachian carbon isotope excursion (CIE) through the Early Toarcian negative CIE. Using a  statistical analysis of all available Karoo and Ferrar Large Igneous Province (LIP ) U-Pb and Ar-Ar radioisotopic ages we create a timeline of the key events and examine the timing of the carbon cycle perturbations specifically looking at potential links to peaks of extrusive emplacement of the Karoo and Ferrar LIP. The geochronological framework is further compared with other available radioisotopic dates from correlative sections, allowing for a more precise constraint and validation of the timing and duration of these Early Jurassic events.

 

How to cite: Al-Suwaidi, A., Ruhl, M., Kemp, D., Storm, M., Hesselbo, S., Jenkyns, H., Mather, T., Percival, L., and Condon, D.: A Southern Hemisphere Chronostratigraphic Framework for the Pliensbachian–Toarcian Carbon Cycle Perturbations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15374, https://doi.org/10.5194/egusphere-egu24-15374, 2024.

08:40–08:50
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EGU24-12015
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ECS
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Virtual presentation
Wahyuningrum Lestari, Aisha Al Suwaidi, Calum Fox, Vivi Vajda, Andrea Ceriani, Yadong Sun, Joost Frieling, and Tamsin Mather

Late Paleozoic Ice Age (LPIA), which peaked during the mid Permian, resulting in widespread ice centers across Gondwana during its coldest periods. Assessing the climate change across this glaciation and the following deglaciation interval contribute important data not only in terms of understanding the end-Permian extinction event but also present-day global change. Tasmania, located in a high-latitude setting, forming a bridge between the continents Antarctica and Australia provides a valuable record of the environmental and climatic shifts that occurred in areas proximal to glaciation during the acme and waning stages of the LPIA.

At the time of glaciation, Tasmania was a distinct landmass located within the Paleo-Antarctic Circle at a paleo-latitude of ~78°S. Here we present new high-resolution bulk organic carbon isotope analyses (δ13CTOC), mercury, bulk and trace elemental and sedimentological data combined with palynology and conodont biostratigraphy from the late stage (P3 and P4) of the LPIA Glacial-Deglacial Episode III. We base the data on samples from the Bicheno-5 core, from Eastern Tasmania, which contains approximately 83 meters of middle Permian glaciomarine sediments.

Three negative carbon isotope excursions (CIEs) have been identified in the middle Permian (mPN1, mPN2, and mPN3). The latter two are correlated with the deglaciation episodes in Eastern Australia's glacial intervals P3 and P4 phases. Diamictites and dropstones are typically present in the sediments that record the most positive carbon isotope values, which likely correspond to the peak of the glaciation period. Elemental proxies indicate two cycles of increased weathering and terrestrial sediment influx to the marine system. These cycles coincide with the most negative carbon isotope values and are associated with deglacial cycles in Tasmania and within the paleo-Antarctic circle. The first deglacial cycle (mPN1) coincides with elevated mercury (Hg/TOC) which may hint at a link between deglaciation and volcanism, possibly from the Tarim III LIP.

Comparisons with similar records from the marine Pingdingshan (PDS) section in South China confirms that our data from Tasmania reflect global carbon cycle perturbations providing new insights into the significant global climatic shifts that occurred during the middle Permian. The end stage of the LPIA offers a unique comparison to modern environmental and climatic change in Antarctica associated with anthropogenic global warming.

How to cite: Lestari, W., Al Suwaidi, A., Fox, C., Vajda, V., Ceriani, A., Sun, Y., Frieling, J., and Mather, T.: Unraveling Tasmania's Late Paleozoic Ice Age: Carbon Isotopic and Stratigraphic Signatures in Response to Glacial-Deglacial Cycles and Large Igneous Province (LIP) Events, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12015, https://doi.org/10.5194/egusphere-egu24-12015, 2024.

08:50–09:00
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EGU24-18433
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On-site presentation
Arpan Dutta and Santanu Banerjee

Gondwana Basins of eastern India preserves sediment record from Carboniferous to Triassic, which were possibly sourced partially from Antarctica through a radial drainage system. This study attempts to test the hypothesis regarding source of sediments based on petrographical and mineral chemical analysis of siliciclastic Paleo-Mesozoic sediments of eastern India. We present an integrated provenance and paleodrainage analysis on the sediments of Bokaro and Raniganj basins, outcrops of which occur along E-W trend along eastern part of India. The sedimentation in these Gondwana basins initiates with basal Talchir Formation, consisting of alternation between conglomerate and fine- to medium-grained sandstones, and is succeeded by Barakar-Barren Measures-Raniganj and Panchet Formation with sandstone-mudstone alternation, with or without coal.  Petrographic study of sandstones reveals moderate sorting, with angular to sub-rounded quartz and feldspar and rounded to well-rounded lithic fragments; however, the abundance of lithic fragments drastically reduces from Talchir to Panchet formation. Feldspar grains shows the dominance of K-feldspar over plagioclase.  Most of the sandstones are classified as feldspatho-quartzose arenite. The Qm-F-Lt plot indicates that these sandstones were derived primarily from transitional continental sources. Heavy minerals in sandstones include garnets, tourmaline, epidote, rutile, zircon, monazite in order of decreasing abundance. Mineral chemistry of garnet in sandstones points their source to metasedimentary amphibolite facies rocks and granitoid. The tourmaline mineral chemistry suggests the derivation of sediments from various sources, including Li-poor granitoids associated with pegmatites, aplites and Ca-poor metapelites. Rutile chemistry in sandstones indicates the predominance of metapelitic source over metamafic source. Insights from heavy mineral analysis indicates that the Gondwana sediments were derived from multiple sources, and such variation in sources bears information about paleogeographic and paleotectonic evolution of the depositional basin.  The mineral composition of source rocks and paleocurrent data tracks the source of sediments to Eastern Granulite-Schist belt and the Eastern Ghat mobile belt, situated to the east and southwest parts of the Gondwana succession.  This study when integrated with geochronological data would reveal the extent to which a particular source provided sediments to these basins, evolution of sediment sources from bottom to top and ultimately will lead to a refined understanding of timing and evolution of East Gondwana assembly.

How to cite: Dutta, A. and Banerjee, S.: Facies Analysis, Petrography, heavy mineral analysis of paleo-Mesozoic sediments of Eastern India: Implications on provenance and basin evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18433, https://doi.org/10.5194/egusphere-egu24-18433, 2024.

09:00–09:10
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EGU24-2721
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ECS
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On-site presentation
Ronghao Wei and Liang Duan

The basal Cambrian sandstone unit in the North China craton (NCC) is an example of globally widespread siliciclastic succession that resides on the Great Unconformity and deposited on a hypothesized low-lying peneplain during the Cambrian global eustatic sea-level rise. Detrital zircon age signatures from this distinct sequence enable recognition of the ancient drainage system of the NCC in deep time and track its potential linkage with the Gondwana landmass. LA-ICP-MS U–Pb dating of the fossil-calibrated basal Cambrian (Series 2) detrital zircon samples from seven measured sections reveal marked spatial changes in their age signatures that can be divided into three distinct types. The first is generally characterized by the bimodal age populations with broad peaks at ~1.85 Ga and ~2.5 Ga that correlate with the Archean to Paleoproterozoic basement inboard of the NCC. The second is featured by multi-modal distribution with diagnostic Neoproterozoic peaks that correspond to subregional magmatic record. The third also shows multiple-zircon age populations, but yields significant crystallization ages close to the early Cambrian age. Comparing our new data with existing age spectra for the Cambrian strata across the NCC and the northern Gondwana demonstrates that separate drainage systems did exist in the peneplained basement during global Cambrian transgression and the basal Cambrian unit in the NCC was not a part of the far-travelled sand sheet across the northern margin of Gondwana. The most suitable source for Cambrian-aged grains constrained by paleogeographic restoration is the arc terrane developed along the northern margin of the NCC as a result of subduction of the Paleo-Asian oceanic plate. Our new continental-scale detrital zircon provenance signatures in the basal Cambrian unit suggest that the NCC should be considered a discrete continental block separated by the Proto-Tethys Ocean in the Cambrian, rather than an integral part of the northern Gondwana.

How to cite: Wei, R. and Duan, L.: Detrital zircon age signatures of the basal Cambrian sandstone unit in North China: implications for drainage divides during global Sauk transgression and separation from Gondwanaland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2721, https://doi.org/10.5194/egusphere-egu24-2721, 2024.

09:10–09:20
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EGU24-15516
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On-site presentation
Valerio Olivetti, Silvia Cattò, Fabrizio Balsamo, Luca Zurli, Matteo Perotti, Gianluca Cornamusini, Marco Fioraso, Federico Rossetti, and Massimiliano Zattin

The Transantarctic Basin is a continental basin system developed for ca 200 Myr, from the Devonian to the Early Jurassic, along the Panthalassa margin of Gondwana and above the peneplained Ross Orogeny rocks. The Beacon Supergroup strata form the clastic sedimentary infill of the Transantarctic Basin.

Geodynamic interpretation of the Transantarctic Basin is not univocal and likely geodynamic conditions accounting for basin subsidence have been changed in space and time. Involvement of the basin into the Gondwanian orogenic deformation is a key question for defining the geodynamic setting and the tectonic environment during the Beacon Supergroup deposition. Nonetheless, involvement of  Beacon Supergroup  in orogenic shortening is  poorly assessed for the limited exposed rocks and because formation of the Cenozoic  Transantarctic rift shoulder modified the Paleozoic geometry of the Beacon strata.

Here we explored the exhumation pattern and thermal evolution of the basement rocks and the immediately overlain Beacon sandstones through low-temperature apatite fission track and (U-Th)/He zircon thermochronology along the Prince Albert Mts, where Beacon deposits are particularly thin to suppose a relevant erosional event during the Paleozoic. Thermochronological data and thermal modelling pointed out that basement rocks and Beacon sandstones of the Prince Albert Mts have preserved evidence of a Late Paleozoic erosional event that allows to infer an actively eroding topographic high that lasted from Early to Late Paleozoic times, as a consequence of the far-field stress transmitted from the active Gondwanian convergent margin.

How to cite: Olivetti, V., Cattò, S., Balsamo, F., Zurli, L., Perotti, M., Cornamusini, G., Fioraso, M., Rossetti, F., and Zattin, M.: Uplift and erosion of an intraforeland topographic high: implication for the evolution of the Gondwanian Transantarctic foreland, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15516, https://doi.org/10.5194/egusphere-egu24-15516, 2024.

09:20–09:30
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EGU24-21597
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ECS
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Highlight
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On-site presentation
The Chon Aike magmatic province: an active margin origin?
Joaquin Bastias-Silva, Richard Spikings, Teal Riley, and Jorge Sanhueza
Geodynamics
09:30–09:40
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EGU24-2858
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ECS
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On-site presentation
Gabriel Robl, Bernhard Schuberth, Isabel Papanagnou, and Christine Thomas

Mantle convection is driven by buoyancy forces in Earth’s interior. The resulting radial stresses generate vertical deflections of the surface, leaving traces in the geological record. Utilizing new data assimilation techniques, geodynamic inverse models of mantle flow can provide theoretical estimates of these surface processes, which can be tested against geological observations. These inverse models are emerging as powerful tools, providing the potential for tighter constraints on the relevant physical parameters governing mantle flow.

The geodynamic inversions mentioned above require an estimate of the present-day thermal state of the mantle, which can be derived from seismic observations. Using thermodynamically self-consistent models of mantle mineralogy, it is possible to convert the seismic structure imaged by global tomographic models to temperature. However, both seismic and mineralogical models are significantly affected by inherent limitations and different sources of uncertainty. In addition, owing to the complexity of the mineralogical models, the relation between temperature and seismic velocities is highly non-linear and not strictly bijective: In the presence of phase transitions, different temperatures can result in the same seismic velocity, making the conversion from seismic heterogeneity to thermal structure non-unique.

We investigate the theoretical ability to estimate the present-day thermal state of the mantle based on tomographic models in the case of isochemical convection. The temperature distribution from a 3-D mantle circulation model with earth-like convective vigour serves as the “true” temperature field. Using a closed-loop experiment, we aim to recover this initial model after: 1) mineralogical mapping from the “true” temperatures to seismic velocities, 2) application of a tomographic filter to mimic the effect of limited tomographic resolution, and 3) mapping of the “imaged” seismic velocities back to temperatures. We test and quantify the interplay of smoothed seismic structure due to tomographic filtering with different approximations for the conversion from seismic to thermal structure. Additionally, owing to imperfect knowledge of the parameters governing mineral anelasticity, we test the effects of changes to the anelastic correction applied in the mineralogical mapping. The observed mismatch between the recovered and initial temperature field is dominated by the effect of tomographic filtering, with a depth-dependent average error of up to 200 K. Additionally, we observe systematic large errors in the vicinity of phase transitions. Our results highlight that, given the current limitations of tomographic models and the incomplete knowledge of mantle mineralogy, magnitudes and spatial scales of a temperature field obtained from global seismic models will deviate significantly from the true state, even under the assumption of purely thermally driven mantle flow. Strategies to estimate the present-day thermodynamic state of the mantle must be carefully selected to minimize additional uncertainties.

How to cite: Robl, G., Schuberth, B., Papanagnou, I., and Thomas, C.: Deriving mantle temperatures from global seismic models: A quantitative analysis in the light of uncertain mineralogy and limited tomographic resolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2858, https://doi.org/10.5194/egusphere-egu24-2858, 2024.

09:40–09:50
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EGU24-10566
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ECS
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On-site presentation
Roman Freissler, Bernhard S.A. Schuberth, and Christophe Zaroli

Interpretations of seismic tomography and applications of the resulting tomographic images, e.g. for estimating present-day mantle temperatures, require information on their resolution and uncertainty. Assessing these model properties is often difficult due to the large size of tomographic systems on global scales. In consequence, there have been only few attempts to consistently analyse the spatially variable quality of tomographic images of deep mantle structure. For linear problems, both resolution and uncertainty can be quantified with the tools provided by classic Backus–Gilbert (B–G) inversion. In this theory, averaging kernels define the local resolving power at each model parameter, while uncertainties represent the propagation of data errors into the model values. By using a more efficient variant of B–G inversion, the method of 'Subtractive Optimally Localized Averages' (SOLA), global tomography can be performed with complete information for model appraisal.

Based on the SOLA framework, we present a concept for the assessment of the 3-D resolution information contained in a global set of averaging kernels. It is based on the rigorous estimation of resolution lengths from a 3-D Gaussian parametrization of the averaging kernels, together with a test for the robustness of this approximation. This is a necessary step because a perfectly bell-shaped or delta-like behaviour of resolution can not always be guaranteed in global tomography due to the inhomogeneous data coverage. Therefore, we also develop a classification scheme, which enables a basic identification of those averaging kernels that are too complex to be sufficiently described by the chosen definition of resolution length. We note that this approach is more generally applicable, i.e. it can be used with any explicitly available set of averaging kernels or point-spread functions, but also with alternative parametrizations.

In the context of the SOLA method, our resolution analysis can be further used to locally calibrate the inversion parameters. This involves on the one hand the specification of a target (resolution) kernel. On the other hand, a trade-off parameter needs to be selected that regulates the fit of the averaging to the target kernel, and the conversely affected propagation of data errors.

To this end, we apply our concept for robust resolution estimation to different sets of averaging kernels from SOLA inversions with varying parameter combinations. Most notably, we systematically increase the spatial extent of the target kernels (taken as 3-D Gaussian functions here as well). The final maps of global (and classified) resolution and uncertainty can be viewed together for a complete picture of the model quality. They reveal where, and for which target size and amount of error propagation, resolution lengths are meaningful and model values can be interpreted appropriately.

How to cite: Freissler, R., Schuberth, B. S. A., and Zaroli, C.: Global assessment of tomographic resolution and uncertainty with the SOLA method, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10566, https://doi.org/10.5194/egusphere-egu24-10566, 2024.

09:50–10:00
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EGU24-10128
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ECS
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On-site presentation
Anna Schneider, Bernhard Schuberth, Paula Koelemeijer, Grace Shephard, and David Al-Attar

Fluid dynamics simulations are a powerful tool for understanding processes in the Earth's deep interior. Mantle circulation models (MCMs), for example, provide important insight into the present-day structure of the mantle and its thermodynamic state when coupled with mineralogical models, which is essential information for other fields in the geosciences. The evolution of the heat flux through the core-mantle boundary, for instance, is a prerequisite for geodynamo simulations that aim to model the reversal frequency pattern of the Earth's magnetic field on geologic time scales. However, geodynamical modelling requires extensive knowledge of deep Earth properties and plate motions over time. Uncertainties in these model inputs propagate into the MCMs, which subsequently have to be evaluated with independent data, such as the seismological or geological record. Although state-of-the-art MCMs typically explain statistical properties of seismological data, they do not consistently reproduce the location of features in the mantle.

In this contribution, we explore the effect of varying the absolute position of mantle structure on seismic data by applying first-order modifications to an initial MCM. Normal mode data are particularly well suited for assessing the resulting changes in the location of mantle structure, as they capture its long-wavelength component throughout the entire mantle. In addition, the global sensitivity of normal modes reduces the drawbacks of uneven data coverage. Specifically, we use two different seismic forward modelling approaches, an iterative direct solution method for computing full-coupling spectra and a splitting function calculation that is based on the self-coupling approximation. Our goal is to quantify the effects of a limited number of large-magnitude earthquakes, the adequacy of the self-coupling approximation, and the resolvability of relevant model differences through a comprehensive data analysis. Our synthetic forward modelling framework is moreover well suited for testing the depth sensitivity associated with specific frequency intervals in the spectrum that generally is inferred from seismic 1-D profiles within the splitting function approximation.

How to cite: Schneider, A., Schuberth, B., Koelemeijer, P., Shephard, G., and Al-Attar, D.: Exploring the potential of normal mode seismology for the assessment of geodynamic hypotheses, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10128, https://doi.org/10.5194/egusphere-egu24-10128, 2024.

10:00–10:10
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EGU24-13895
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solicited
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Highlight
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Virtual presentation
Juliane Dannberg, Zachary Eilon, Joshua B Russell, and Rene Gassmoeller

Understanding the interaction between oceanic plates and the underlying asthenosphere and its impact on plate thickness is essential for explaining plate motions and mantle convection patterns. While sub-lithospheric small-scale convection provides an explanation for why oceanic plates do not continue to thicken after a certain age, many open questions still surround this process. Here, we link dynamic models of mantle flow, grain-scale processes, seismic imaging, and surface observations to gain new insights into the mechanisms of asthenospheric small-scale convection and its surface expressions.

We have performed a series of high-resolution 3D numerical models of the evolution of oceanic plates and the development of thermal instabilities at their base using the open-source geomodeling software ASPECT. These simulations use an Earth-like rheology that includes coupled diffusion and dislocation creep as well as their interplay with an evolving olivine grain size. Our models quantify how the effective asthenospheric viscosity and the balance between diffusion and dislocation creep affect the morphology and temporal stability of small-scale sub-lithospheric convection, including the age of its onset, the average depth and wavelength of the small-scale convection rolls, and the amplitude of the temperature and grain size anomalies within the rolls.

All of these quantities predicted by the dynamic models can be directly related to both geophysical observables and to surface manifestations such as dynamic topography and heat flux. To accurately compare our model outputs to geophysical data, we convert them to seismic velocity and attenuation using laboratory-derived constitutive relations and taking into account variations in temperature, pressure, grain size, water content and calculated stable melt fraction. We then create synthetic seismic tomography models of different dynamic scenarios and analyze their fit to observations from the Pacific OBS Research into Convecting Asthenosphere (ORCA) experiment. Comparison with both seismic imaging and surface expressions allows us to determine the parameter range in which geodynamic models fit these observations, providing new constraints on the convection patterns and the rheology of the oceanic asthenosphere beneath the Pacific Plate.

How to cite: Dannberg, J., Eilon, Z., Russell, J. B., and Gassmoeller, R.: Sub-Lithospheric Small-Scale Convection as a Window into the Asthenosphere: Insights from Integrating Models Of Mantle Convection, Grain Size Evolution and Seismic Tomography, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13895, https://doi.org/10.5194/egusphere-egu24-13895, 2024.

10:10–10:15
Coffee break
Chairpersons: Megan Holdt, Sergei Lebedev, Ingo L. Stotz
10:45–10:55
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EGU24-16531
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ECS
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On-site presentation
Menno Fraters, Magali Billen, John Naliboff, Lydia Staisch, and Janet Watt

The Cascadia Subduction Zone is characterized by young subducting lithosphere, its isolation from other subducting systems, and its ability to produce megathrust earthquakes (M>9.0) and devastating tsunamis. Due to its high potential hazard and risk, it is also a well-studied subduction zone where modern, diverse and detailed observational datasets are available through the USGS and initiatives like GeoPrisms and EarthScope. These datasets include high quality GPS, onshore and offshore geophysical imaging, geochemical and seismic anisotropy data. Integrating these data sets with geodynamic modeling presents an opportunity to gain insight into outstanding questions regarding slab structure, tectonic evolution, seismic hazards, and the physical processes that can self-consistently explain all these observations. For example, geologic and geophysical data suggest that there may be one or two prominent slab gaps or tears, while tomographic data does not fully constrain the depth extent of the slab. Furthermore, the overriding plate is composed of different terranes and contains numerous active and slowly moving faults, complicating efforts to accurately constrain variations in present-day stress and deformation rates.

In this study we test whether comparison of observations to geodynamic model predictions can distinguish between different slab geometries for the Cascadia Subduction Zone. To this end, we have created regional 3D geodynamic models of Cascadia including the slab based on the Slab 2.0 dataset. The model setup is built with the Geodynamic World Builder, and the models are run with the geodynamics code ASPECT. We present results which compare the Juan de Fuca plate velocities against the present day Euler poles. We have found that matching the plate velocity magnitude and direction is sensitive to the rheological model overall, while at the same time being insensitive to certain aspects of the plate boundary rheologies. During the evolution of these models we track the development of the CPO (Crystal Preferred Orientation) with an implementation of the DREX algorithm, so we can compare it against observations of seismic anisotropy in the region. Our presentation will focus on the importance of the geometry of the slab and the strength of different sections of the interface. Furthermore, these models and demonstrate workflows for linking the model results to surface tectonics.

How to cite: Fraters, M., Billen, M., Naliboff, J., Staisch, L., and Watt, J.: Exploring the structure of the Cascadia Subduction Zone by coupling 3D thermomechanical modeling and CPO evolution with observations., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16531, https://doi.org/10.5194/egusphere-egu24-16531, 2024.

10:55–11:05
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EGU24-18172
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On-site presentation
Ana M. Negredo, Javier Fullea, Olga Ortega-Gelabert, Carlos Clemente, and Julien Babault

The topography of the Iberian Meseta located between the Pyrenees-Cantabrian Mountains and the Betics Chain is moderately high (660 m on average) compared to the high plateaus on Earth (> 1 km) albeit higher than the topography of the surrounding western European plate. The Iberian Meseta encompasses Cenozoic sedimentary basins, active or inactive Alpine mountain ranges, and low-relief erosional surfaces represented by plateaus with elevations between 600 and 1400 m asl. It is commonly accepted that ~600-700 m surface uplift occurred during the Cenozoic, but the underlaying processes and the precise timing of the onset of the plateau growth are strongly debated. The main objective of the present study is to find out to what extent the topography of the Iberian Meseta has a crustal, lithospheric or a sublithospheric origin. We used the results of a recent modelling based on the joint inversion of both the crustal and lithospheric mantle structure. It encompasses an integrated geophysical-lithological multi-data modelling. The inversion is framed within an integrated geophysical-petrological setting where mantle seismic velocities and densities are computed as a function of temperature and composition whereas crustal density, shear and compressional wave velocities are lithologically linked based on empirical relationships from global petrophysical databases.

We computed the relative contribution to topography of crustal and lithospheric mantle thickness variations and density structure. The topography of the Alpine mountain belts in Iberia is largely associated with thickened crust. We find that the elevated topography in the NW Iberian Meseta (elevation > 700 m) is mostly related to the lithospheric mantle thinning. This is in agreement with Inversion of topographic data, landform dates, and erosion rates suggesting a late Cenozoic mantle-related surface uplift of several hundreds of meters in NW Iberia (EGU24-11613) and in the central Iberia (EGU24-16382). Similarly, a thin and warm lithospheric mantle is responsible for the positive elevation of the onshore Mediterranean margins. A negatively buoyant lithospheric mantle causes >1 km subsidence in the Gibraltar Arc and western Pyrenees.  We solved the Stokes flow to evaluate the contribution of temperature-related buoyancy forces at asthenospheric depths. These forces cause a long wavelength topographic response located in the centre of the Iberian Peninsula reaching a maximum value of only 100-150 m, which is much lower than the values reported in previous works assuming an isostatic balance.

How to cite: Negredo, A. M., Fullea, J., Ortega-Gelabert, O., Clemente, C., and Babault, J.: On the different contributions to the peculiar topography of the Iberian Peninsula, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18172, https://doi.org/10.5194/egusphere-egu24-18172, 2024.

11:05–11:15
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EGU24-12118
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ECS
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On-site presentation
Berta Vilacís, Hamish Brown, Sara Carena, Hans-Peter Bunge, Jorge N. Hayek, Ingo L. Stotz, and Anke M. Friedrich

Mantle convection is a fundamental process governing the evolution of our planet. Buoyancies in the mantle induce horizontal and vertical motion of the Earth’s lithosphere, which can be mapped using independent geological datasets. Positive surface deflections induced by mantle convection create erosional/non-depositional environments which lead to gaps (hiatuses) in the stratigraphic record, while negative deflections provide accommodation space for sedimentation to occur. We use continental- and country-scale digital geological maps and regional and local stratigraphic studies at the temporal resolution of geological series (ten to tens of millions of years) to map the distribution of hiatus through geological time.

Here we present global continental hiatus surfaces since the Upper Jurassic. We find that they vary inter-regionally at timescales of geological series and that they correlate with known mantle dynamic events. For example, we tend to observe the appearance of a hiatus surface before the arrival of a mantle plume. In Europe, we mapped a large-scale sedimentary hiatus during the Paleocene, prior to the arrival of the Iceland plume. In Africa and South America, we found a widespread absence of the Upper Jurassic prior to the arrival of the Tristan plume. This pattern can be seen as characteristic of plume-induced dynamic uplift. We observe a sea level signal during some geological series, such as in the Oligocene, when there is a global increase of hiatus areas, coinciding with the onset of Antarctic glaciation and associated sea level drop. At other times, we find that the hiatus areas evolve differently for different continents, precluding their interpretation as an eustatic signal. Spectral analysis shows that hiatus surfaces have shorter wavelengths than no hiatus surfaces, requiring higher spherical harmonic degrees to describe the geological series with larger amounts of hiatus. These include the Upper Jurassic, the Paleocene, the Oligocene and the Pleistocene.

Our results imply that a key property of time-dependent geodynamic Earth models must be a difference in timescale between mantle convection itself and resulting dynamic topography. Moreover, they highlight the importance of continental-scale compilations of geological data to map the temporal evolution of mantle flow beneath the lithosphere, which can provide powerful constraints for global geodynamic models.

How to cite: Vilacís, B., Brown, H., Carena, S., Bunge, H.-P., Hayek, J. N., Stotz, I. L., and Friedrich, A. M.: Global continental hiatus surfaces as a proxy for tracking dynamic topography since the Upper Jurassic, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12118, https://doi.org/10.5194/egusphere-egu24-12118, 2024.

11:15–11:25
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EGU24-4552
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ECS
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Highlight
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On-site presentation
Hamish Brown, Berta Vilacís, Ingo Stotz, Yi-Wei Chen, and Hans-Peter Bunge
The transient uplift and subsidence of the Earth’s surface induced by mantle convection (dynamic topography) leaves an imprint on the stratigraphic record at inter-regional scales. Dynamically uplifted continental regions result in widespread erosional/non-depositional environments (sedimentary hiatus), while subsided regions result in continuous sedimentation. Thus, by mapping hiatus and no-hiatus signals on inter-continental scales, one gains a proxy for the long-wavelength uplift and subsidence associated with dynamic topography. In this contribution, we report on the use of hiatus maps as a constraint on mantle circulation models (MCMs), which make predictions of the history of dynamic topography. In order to make such a comparison, we filter the modelled dynamic topography through the available data points from the real maps to form hiatus/no hiatus signals. The resulting synthetic hiatus maps are then directly comparable to the true maps. By generating synthetic hiatus maps for a variety of high-resolution TERRA MCMs, we show that such maps allow for the falsification or verification of MCMs based on their prediction of dynamic uplift/subsidence events. We additionally find that eustatic sea-level variations are clearly highlighted by geological series in which the global ratio of hiatus/no-hiatus surfaces is significantly over-/under-predicted by the synthetic maps. We stress that, while plume histories in MCMs are constrained only by the surface tectonic history, this form of comparison paves the way for the validation of adjoint geodynamic models in which plume histories are constrained by seismic tomography.

How to cite: Brown, H., Vilacís, B., Stotz, I., Chen, Y.-W., and Bunge, H.-P.: Synthetic Hiatus Maps as a Tool for Constraining Global Mantle Circulation Models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4552, https://doi.org/10.5194/egusphere-egu24-4552, 2024.

11:25–11:35
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EGU24-18733
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On-site presentation
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Andrea Sembroni, Claudio Faccenna, Thorsten W. Becker, and Paola Molin

The East Africa - Arabia topographic swell is an anomalously high-elevation region of ~4000 km long (from southern Ethiopia to Jordan) and ~1500 km wide (from Egypt to Saudi Arabia) extent. The swell is dissected by the Main Ethiopian, Red Sea, and Gulf of Aden rifts, and characterized by widespread basaltic volcanic deposits emplaced from the Eocene to the present. Although most agree that mantle plumes play a role in generating the swell, several issues including the number and locations of plumes and the uplift signatures remain debated. We seek to address these questions and provide a general evolutionary model of the region. To this end, we conduct a quantitative analysis of topography to infer isostatic and dynamic contributions. When interpreted jointly with geological data including volcanic deposits, the constraints imply causation by a single process which shaped the past and present topography of the study area: the upwelling of the Afar superplume. Once hot mantle material reached the base of the lithosphere below the Horn of Africa during the Late Eocene, the plume flowed laterally toward the Levant area guided by pre-existing discontinuities in the Early Miocene. Plume material reached the Anatolian Plateau in the Late Miocene after slab break-off and the consequent formation of a slab window. During plume material advance, buoyancy forces led to the formation of the topographic swell and tilting of the Arabia Peninsula. The persistence of mantle support beneath the study area for tens of million years also affected the formation and evolution of the Nile and Euphrates-Tigris fluvial networks. Subsequently, surface processes, tectonics, and volcanism partly modified the initial topography and shaped the present-day landscape.

How to cite: Sembroni, A., Faccenna, C., Becker, T. W., and Molin, P.: The uplift of East Africa-Arabia swell: the signature of the mantle upwelling and spreading, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18733, https://doi.org/10.5194/egusphere-egu24-18733, 2024.

11:35–11:45
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EGU24-21895
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Highlight
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On-site presentation
Hans-Peter Bunge, Ingo L. Stotz, Nicolas Hayek, berta vilacis, hamish brown, roman freissler, bernhard schuberth, sara carena, and anke friedrich

Recent advances in computational capabilities make it possible to compute global geodynamic earth models at near earthlike convective vigor. This paves the way to systematically obtain a range of synthetic data from such models in an approach that is known as closed loop experiments. Here we present results from closed loop experiments in geodynamic earth models targeted at three classes of data that are sensitive to the mantle convection process, namely seismic data, global stress patterns as reflected by the world stress map, and continent scale stratigraphy processed for the distribution of conformable and unconformable successions in recently developed so called hiatus maps. Our results reveal effects from spatially variable data collection and quality (as expected), mantle flow geometries (less expected) and (still poorly known) histories of paleo mantle flow. We conclude that the derivation of process based synthetic data from geodynamic earth models provides crucial information for data interpretion, that closed loop experiments are
a powerful tool to link geodynamic earth models to data, and that closed loop experiments could be helpful to guide future data collection efforts.

How to cite: Bunge, H.-P., Stotz, I. L., Hayek, N., vilacis, B., brown, H., freissler, R., schuberth, B., carena, S., and friedrich, A.: Closed loop experiments in global geodynamic earth models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21895, https://doi.org/10.5194/egusphere-egu24-21895, 2024.

11:45–11:55
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EGU24-3083
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ECS
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On-site presentation
Yi-Wei Chen, Hans-Peter Bunge, Ingo Stotz, and Jonny Wu

Global plate reconstructions that constrain the surface plate motions provide crucial boundary conditions for mantle circulation models. Earth-like plate kinematics could reduce the impact of the uncertain mantle initial conditions and generate slab structures in the mantle that are comparable with seismic tomographies. However, due to the subduction of the oceanic plates, uncertainty increases in global plate reconstruction over time. Here, we utilize a novel slab unfolding technique to retrodeform mantle slabs imaged in the MITP08 seismic topography back to the pre-subduction states at Earth’s surface. Such a technique provides additional constraints on plate reconstructions, especially in regions dominated by intra-oceanic subductions, such as Southeast Asia.

Our reconstruction shows a significant trench retreat along Southeast Asia and Northern Australia between 90 and 65 Ma that opened a gigantic, >3,000 km wide backarc basin. This basin, named the East Asian Sea plate, was later consumed by the west-moving Philippine Sea plate and North-moving Australian plate in the Cenozoic. We then embed our reconstruction in a mantle circulation model, TERRA, testing the fidelity of the reconstruction in a closed-loop experiment.

We found that fragmented, sub-horizontal East Asian Sea slabs can be reproduced in the mantle circulation model. These slabs lying underneath the current Philippine Sea plate and northern Australia are similar to the MITP08 tomography on which the reconstruction is built. Moreover, these slabs at 800-1000 km depths result in a more negative dynamic topography on the present Philippine Sea plates comparable with the observed residual topography. On the contrary, the traditional, Andean-style reconstruction can only produce positive dynamic topography. Other Mesozoic, intra-oceanic subductions in NE Asia and western North America embedded in our reconstruction also produce negative, yet smaller magnitude, dynamic topography, possibly due to the older subduction history and deeper slabs. We conclude the negative dynamic topography within the present Pacific plate is the result of ancient intra-oceanic subductions. 

How to cite: Chen, Y.-W., Bunge, H.-P., Stotz, I., and Wu, J.: Testing tomography-based plate reconstructions from a paired, inverse-forward closed-loop experiment in a mantle circulation model, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3083, https://doi.org/10.5194/egusphere-egu24-3083, 2024.

11:55–12:05
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EGU24-9346
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Highlight
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On-site presentation
An Yang, Anthony Watts, and Shijie Zhong

It is widely recognized that mantle dynamics and plate flexure both contribute to Earth’s topography and gravity fields at different wavelengths, yet the actual transition wavelength between them is not well quantified, ranging from ~100 km to ~1000 km. Here we use the observed relationship between topography and the free-air gravity anomaly fields (admittance) to infer the relative contribution of plate flexure and mantle dynamics based on mantle flow models which incorporate an essentially elastic plate. Global and regional Pacific Ocean data studies show that plate flexure and mantle convection potentially contribute to the topography and gravity for wavelengths larger than ~600 km. Plate flexure mainly contributes at wavelengths shorter than ~600 km and is consistent with the support of uncompensated topography for wavelengths shorter than ~200 km. To investigate the admittance associated with mantle dynamics at long wavelengths we have constructed mantle flow models based on a number of different seismic tomography models. The finite element software CitcomS was used to calculate mantle flow and related surface dynamic topography and associated free-air gravity anomaly. Admittance analysis in the Pacific Ocean from different mantle flow models show that the dynamic admittance is generally larger than the observed admittance, while the admittance from plate flexure is smaller than the observed admittance, suggesting that both mantle dynamics and plate flexure contribute to Earth’s topography and gravity at long-wavelengths. The difference between the dynamic admittance and the observed admittance is smallest for cases with temperature-dependent viscosity and weak asthenosphere, and the combined admittance in the presence of both flexure and mantle convection for these cases is generally consistent with the observed admittance. We use a new method to separate the effects of plate flexure and mantle convection to the topography and gravity fields at long wavelengths which has been developed from the plate flexure and dynamic admittances. We assume that the topography and gravity at long wavelength are the combination of plate flexure and mantle dynamics and further assume that the topography and gravity are linearly related through the admittance. The final separated dynamic topography in the Pacific Ocean is generally consistent with previously published residual topography studies at long-wavelengths.

How to cite: Yang, A., Watts, A., and Zhong, S.: Long-wavelength gravity and topography of the Pacific Ocean: Relative contribution of mantle dynamics and plate flexure , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9346, https://doi.org/10.5194/egusphere-egu24-9346, 2024.

12:05–12:15
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EGU24-12457
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ECS
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On-site presentation
Shayan Kamali Lima, Alessandro M. Forte, and Marianne Greff

While the isostatic compensation of crustal thickness and density heterogeneity provides the dominant contribution to Earth’s observed topography, there nonetheless remains a substantial difference (the ‘residual topography’) between these two fields. This difference is a consequence of dynamic processes occurring within the mantle, most notably due to time-dependent vertical surface stresses driven by mantle convection. Mantle convection dynamics also produce differences between the observed geoid and the isostatic geoid generated by crustal heterogeneity: the ‘residual geoid’. The joint consideration of both residual geoid and topography anomalies provides unique and fundamental global constraints on the amplitude and spatial distribution of density anomalies in the convecting mantle.
Despite the crucial role of isostasy in determining residual geoid and residual topography, accurate constraints depend heavily on the quality of the isostasy calculations. The classical theory of isostasy relies on a 1st-order treatment of hydrostatic equilibrium, which is not sufficiently accurate for the calculation of isostatic geoid anomalies on a compressible, self-gravitating mantle. Consequently, we present a geodynamically consistent approach that is based on the surface loading response (via dynamic kernels) calculated with a viscous flow model that incorporates a fully compressible mantle and core (given by the PREM reference model) with self-gravitation.
Another critical issue that remains outstanding is the accuracy inherent in global crustal heterogeneity models. Here we show that the differences between the residual geoid and topography fields predicted using CRUST1.0 (Laske et al. 2012) and the most recent ECM1 (Mooney et al. 2023) crustal heterogeneity models are substantial. We discuss the importance and implications of these differences in the context of determining the most accurate constraints on density anomalies in the convecting mantle.

How to cite: Kamali Lima, S., Forte, A. M., and Greff, M.: A Geodynamically Consistent Approach to Residual Topography and Geoid Anomalies on the Convecting Mantle: Importance of Global Crustal Models , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12457, https://doi.org/10.5194/egusphere-egu24-12457, 2024.

12:15–12:25
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EGU24-6721
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Highlight
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On-site presentation
Clinton P. Conrad and Florence Ramirez

Deflection of the Earth’s surface supported by mantle flow, known as dynamic topography, is associated with a free-air gravity anomaly because such topography is not isostatically compensated. Consequently, the ratio of the gravity anomaly to the dynamic topography, known as the admittance, has been used to estimate the amplitude of dynamic topography, which can be difficult to measure directly. However, at long wavelengths (e.g., spherical harmonic degrees 2 to 6) both dynamic topography and gravity anomalies, and thus the admittance, are sensitive to the mantle’s viscosity structure. Previous studies [e.g., Colli et al., 2016] demonstrate a reversal in sign of the free-air gravity anomaly resulting from lower mantle structures as the viscosity of the lower mantle is increased. This indicates potential complexity for inferring long-wavelength dynamic topography from observations of gravity anomalies, because the upper-lower mantle viscosity contrast is poorly constrained. We further investigated the relationship between dynamic topography and gravity anomalies by introducing lateral viscosity variations into a finite element model of global mantle flow. We find that the gravity anomaly above lower mantle density heterogeneity can change dramatically as we begin to introduce different models for lateral viscosity variations into the upper and lower mantle viscosity fields. In such models we find that the sign of the admittance varies laterally, with the horizontal gradients in mantle viscosity perturbing mantle flow patterns in ways that produce large changes gravity anomalies and smaller changes in dynamic topography. A spatially-varying admittance will greatly complicate estimation of dynamic topography from observed gravity, and may help to explain mismatches between observations of dynamic topography and predictions made using global mantle flow models. On the other hand, the reconciliation of such mismatches may help to constrain viscosity heterogeneity in the lower mantle.

Colli, L., S. Ghelichkhan, and H. P. Bunge (2016), On the ratio of dynamic topography and gravity anomalies in a dynamic Earth, Geophysical Research Letters, 43(6), 2510-2516, doi:10.1002/2016GL067929.

How to cite: Conrad, C. P. and Ramirez, F.: Sensitivity of Long-Wavelength Dynamic Topography and Free-Air Gravity to Lateral Variations in Lower Mantle Viscosity, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6721, https://doi.org/10.5194/egusphere-egu24-6721, 2024.

12:25–12:30
Lunch break
Chairpersons: Matthieu Kervyn, Daniel O'Hara, Ingo L. Stotz
14:00–14:10
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EGU24-2321
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ECS
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On-site presentation
Zhirui Ray Wang, Ingo L. Stotz, Hans-Peter Bunge, Berta Vilacís, Jorge N. Hayek, Sia Ghelichkhan, and Sergei Lebedev

Mantle convection is an essential component of the Earth system. Yet its history is not well known , in part, as the strength of tectonic plates conceals the underlying flow. To date, global mantle convection models have reached an impressive level of sophistication due to significant advancement of computational infrastructures and numerical techniques. This ultimately allows geodynamicists to reconstruct past mantle states through using, for instance, inverse geodynamic models based on adjoint equations. However, key input parameters of these models --- such as thermo-chemical flow properties and rheology --- are complex and poorly known. This in turn limits their ability to effectively interpret the reconstructed mantle flow, thus motivating one to pursue an approach that aims to conceptualize paleo-mantle-flow at a simple analytical level.

To this end, the existence of thin, mechanically weak asthenosphere permits one to develop an analytical Couette/Poiseuille model of asthenospheric flow, where flow is associated with moving tectonic plates, and with lateral pressure gradients due to rising plumes and sinking slabs. Here we present estimates of the Cenozoic asthenospheric flow history from such models in the Atlantic realm. We, moreover, link them to azimuthal seismic anisotropy as well as mantle flow retrodiction simulated by inverse geodynamic models. Our analytically derived asthenospheric flow indicates that it is in broad agreement with the orientation of seismic azimuthal anisotropy, and with the large-scale flow patterns from mantle flow retrodictions. In light of these results, our study suggests exploiting a hierarchy of geodynamic models together with growing observational constraints on mantle flow induced surface expressions to gain a better understanding of paleo-mantle-flow.

How to cite: Wang, Z. R., Stotz, I. L., Bunge, H.-P., Vilacís, B., Hayek, J. N., Ghelichkhan, S., and Lebedev, S.: Cenozoic asthenospheric flow history in the Atlantic realm: Insights from Couette/Poiseuille flow models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2321, https://doi.org/10.5194/egusphere-egu24-2321, 2024.

14:10–14:20
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EGU24-6544
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On-site presentation
Peter Japsen, Paul F. Green, Johan M. Bonow, and James A. Chalmers

Peninsula India and Scandinavia are elevated passive continental margins (EPCMs) characterized by asymmetric relief with high mountains in the west and a gentle slope towards lowlands in the east.

New AFTA data from southern India reveal major Phanerozoic episodes of cooling, reflecting exhumation. Here we focus on the early Miocene episode possibly related to the hard India-Asia collision (van Hinsbergen et al. 2012). The Miocene exhumation resulted in a low-relief landscape; e.g. the Karnataka and Mysore plateaus (Gunnel and Fleitout, 1998) with residual regions of higher ground (e.g. Palani Hills). Today, these plateaus reach an elevation of 1 km along the coast of SW India, sloping towards the east. The Miocene peneplains were graded towards the base level of the adjacent ocean (Green et al. 2013), and therefore reached their present elevation after their formation. Thick piles of Pliocene sediments off SW India (Campanile et al. 2008) suggests that this happened during the Pliocene.

Richards et al. (2016) studied river profiles in Peninsula India and concluded that the regional tilt grew since 25 Ma, maintained by sub-lithospheric processes. However, we find that the relief is the result of two episodes: 1) Miocene peneplanation related to far-field stress. 2) Late Neogene, asymmetric uplift driven by sub-lithospheric processes.

We identified a similar development in SW Scandinavia, where two Neogene episodes of uplift and erosion define main features of the relief (Japsen et al. 2018): 1) Early Miocene uplift leading to formation of the Hardangervidda peneplain (possibly related to the hard India-Asia collision). 2) Uplift beginning in the Pliocene, raising Hardangervidda to its present elevation at 1.2 km. Pliocene uplift raised margins around the NE Atlantic with maximum elevations reached close to Iceland. This suggests support from the Iceland Plume due to outward-flowing asthenosphere extending beneath the conjugate margins (Rickers et al. 2013; Japsen et al. 2024). 
Lithospheric as well as sub-lithospheric processes appear to shape main features of EPCMs.

Campanile et al. 2008. Basin Research. Green et al. 2013. GEUS Bull. Gunnell, Fleitout 1998. ESPL. Japsen et al. 2018. JGSL. Japsen et al. 2024. ESR. Richards et al. 2016. G cubed. Rickers et al. 2013. EPSL.

How to cite: Japsen, P., Green, P. F., Bonow, J. M., and Chalmers, J. A.: The large-scale landscapes in SW Scandinavia and in SW India are the result of two episodes of Neogene uplift, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6544, https://doi.org/10.5194/egusphere-egu24-6544, 2024.

Geomorphology of Volcanoes
14:20–14:30
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EGU24-2023
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solicited
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Highlight
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On-site presentation
Thomas R. Walter, Claire E. Harnett, Valentin R. Troll, and Michael J. Heap

Calderas are steep morphological and collapse basins that continue to reshape long after initial structural collapse. While large landslides are associated with caldera collapse and widen the basin, little is known about the morphological and structural changes that occur long after caldera formation. Here, we investigate the shape and slope of the Tambora caldera in Indonesia, which formed in 1815 during one of the most devastating eruptions of the past  centuries. The release of over 150 cubic kilometers of volcanic ash created a caldera 6 kilometers wide and 1250 meters deep, causing climatic effects worldwide. Here we explore an ultra-high-resolution dataset we generated from Pleiades, a tri-stereo satellite, that now allows us to apply computer vision approaches to study the morphology and geometry of the Tambora caldera. We generated a 12 million pixel point cloud resampled to a 1 m resolution Digital Elevation Model and a 0.5 m orthomosaic. We explore the dimension, slope, and outline of the caldera and find localized open fissures, tension cracks, and morphological scars. We also apply an unsupervised image classification approach to the stereo multispectral data and find locations of fumarole activity and hydrothermal alteration in close proximity to these structural features. Hydrothermal alteration sites are commonly located in the caldera wall below the scars and open fissures. We explore this proximity of alteration, scarring, and faulting using newDistinct Element Method models, emphasizing that caldera morphology and structure is strongly influenced by hydrothermal weakening that causes flank instability, localized shedding of material, and large-scale morphological changes.

How to cite: Walter, T. R., Harnett, C. E., Troll, V. R., and Heap, M. J.: Morphology, structure and gravitational instability of the steep caldera walls of Tambora (Indonesia) influenced by hydrothermal alteration., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2023, https://doi.org/10.5194/egusphere-egu24-2023, 2024.

14:30–14:35
14:35–14:45
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EGU24-4176
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ECS
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On-site presentation
Annie Borch, James Kelly Russell, Rene Barendregt, and Pierre Friele

The Cheakamus basalts are a set of ~31 km long, 1.65 km3 valley-filling olivine basalts which erupted into the glaciated Callaghan-Cheakamus Valley system of the Garibaldi Volcanic Belt (GVB), British Columbia. Combined paleomagnetic and radiometric (40Ar/39Ar) analysis dates the lavas as a short-lived (< 2 ka duration) eruption at 15.95 ± 7.9 ka (2σ); additional field evidence, including well-glaciated lava flow surfaces overlain by till, indicate the eruption coincided with the early stages of the Fraser Glaciation (LGM) at ~20-18 ka. The lavas preserve features indicative of a landscape hosting diverse and dynamic paleoenvironments. Subaerial eruption of basalt lava filled an ice-free Callaghan Creek drainage system before inundating and damming of the paleo-Cheakamus River, creating an upstream rising body of water. Periodic overtopping of the lava dam resulted in syn-eruptive intermittent flooding and overtopping of lavas expressed by discontinuous lenses of interflow sediment and well-developed entablatures in the upper portions of lava flows. Rare instances of enigmatic cooling columns indicate localized ice contact with glaciers that partially filled the Cheakamus Valley. Emplacement features and morphologies in the Cheakamus Valley have been heavily altered by the erosional overprinting of a glacial lake outburst flood (GLOF) that preliminary 10Be analysis dates at the close of the LGM (11-10 ka). Lavas in the Callaghan valley remain untouched by the GLOF. Their aerial extent and distribution, especially at high elevations in tributary valley mouths suggest bottlenecking and backing-up of lavas due to narrowing in valley topography. Current work combines field mapping and analogue modelling and aims to provide insight into the emplacement dynamics of effusive lavas in the steep, confined terrain of the BC Coast Mountains. Despite, and in part because of, their heavily modified morphology, the Cheakamus basalts act as an excellent recorder of both effusive volcanic processes and the paleoenvironments into which they erupted. Their thorough and accurate analysis is especially pertinent temporally, as they erupted during a time of glacial flux and can provide additional evidence for the timing and location of the advancing Cordilleran ice sheet. Spatially, the Cheakamus basalts are proximal to population centers and transport infrastructure and thus have implications for potential volcanic hazards and attendant risks, as any future effusive, valley-filling basaltic eruption from the GVB will likely share similar emplacement characteristics and processes.

How to cite: Borch, A., Russell, J. K., Barendregt, R., and Friele, P.: Emplacement and erosion of valley-filling basalt lavas in shifting Quaternary environments of the Garibaldi Volcanic Belt, British Columbia, Canada, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4176, https://doi.org/10.5194/egusphere-egu24-4176, 2024.

14:45–14:55
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EGU24-6885
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On-site presentation
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Servando De la Cruz-Reyna, María Cristina Zarazúa-Carbajal, Gema Victoria Caballero-Jiménez, and Ana Teresa Mendoza-Rosas

A region located in the SW sector of the Michoacán-Guanajuato monogenetic field, in central Mexico displays a high spatial density of scoria cones, mostly around Tancítaro, a large central volcano active in the middle Pleistocene. This region became well known when in 1943 a new volcano, Paricutin, was formed in a cornfield at 11 km to the NW of the extinct stratovolcano. The birth of Paricutin was preceded by significant swarm-type seismicity. Afterward, new seismic swarms were reported in the area in 1997, 1999, 2000, 2006, 2020, 2021, 2022, and 2023, with a mean recurrence interval of only 4 yr, most of them (not all) showing the characteristics of a magmatic origin.  Aiming to shed some light on the relation between the high density of monogenetic cones and the recurrent seismicity, we have made a morpho-chronometric estimate of the relative ages of 170 scoria cones located in the Paricutin-Tancítaro region (PTR) within latitudes 19°N and 20°N and longitudes -102.0° E and -102.7° using the Average Erosion Index (AEI) which quantifies the degree of alluvial erosion of scoria cones from a Fourier analysis of their level contours. Monogenetic activity began in the PTR at about 1 Ma, and the AEI analysis shows that such activity increased after the end of the Tancítaro activity, around 232 ka, and further increased in the Holocene when about one-third of the scoria cones in the region were formed, with a mean interval between eruptions between 120 and 240 yr. On the other hand, a detailed study of two of the most energetic seismic swarms, recorded in 2020 and 2021 shows that the magma intrusion volume required to produce the measured cumulative seismic moment of both swarms amounts to about 140 million cubic meters, which is seemingly insufficient to produce a Paricutin-size eruption, which ejected about 1.3 cubic km of magma. We thus propose a possible conceptual explanation of the recurrent emplacement of monogenetic volcanoes and the frequent seismic swarm activity in terms of a persistent magma source under the crustal extension of the PTR producing numerous dike and sill forming intrusions. In some cases, such intrusions may have a cumulative effect forming temporary magma reservoirs capable of producing new monogenetic eruptions. Assuming that about 0.5 to 1 cubic kilometer of magma needs to accumulate to begin an eruption, about 7 to 14 sizable (similar to the 2020-2021) swarms may then represent a significant precursor.    

How to cite: De la Cruz-Reyna, S., Zarazúa-Carbajal, M. C., Caballero-Jiménez, G. V., and Mendoza-Rosas, A. T.: Cumulative storage of magma in the Paricutin-Tancítaro region, Mexico, revealed by recurrent swarm seismicity and a high spatial density of morpho-chronometrically dated Holocene monogenetic cones., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6885, https://doi.org/10.5194/egusphere-egu24-6885, 2024.

14:55–15:05
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EGU24-2631
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Highlight
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On-site presentation
Loraine Gourbet, Sean F. Gallen, Vincent Famin, Laurent Michon, Miangaly Olivia Ramanitra, and Eric Gayer

The influence of climate on landscape evolution in natural settings remains debated. Here, we focus on tropical hotspot volcanic islands because they exhibit relatively uniform lithology and experience significant precipitation and climate gradients. Furthermore, intermittent volcanic flows effectively “reset” the landscape that begins to evolve post-eruption. Thus, we can constrain initial conditions by reconstructing the initial geometry of radiometrically dated volcanic flows. We constrain landscape evolution through time in several volcanic islands with strong climate gradients to assess the role of climate on incision. We perform topographic reconstructions to calculate long-term basin-averaged erosion rates in two islands of the Réunion hotspot (Réunion, Mauritius) and compile published erosion rates on Réunion and Kaua’i (Hawaii hotspot). We define the time since incision started as the age of the surface incised lava flow. To calibrate incision parameters on all three islands, we use the stream power model and apply a data-driven Bayesian approach to obtain the erodibility, K, the drainage area exponent, m, and the slope exponent, n. We also calculate a normalized erodibility index, Kn, using n = 1 to directly compare results among the different study sites. Erosion rates of Réunion Island range from 9.9 ± 0.5 mm/yr to 5.2 x 10-3 ± 2 x 10-4 mm/yr and erosion rates in Mauritius Island range from 6.5 x 10-2 ± 8 x 10-3 mm/yr to 5.1 x 10-3 ± 4 x 10-4 mm/yr. Incision efficiency seems to decrease with time since incision started from 63 ka to ~300 ka and then does not vary significantly with time since incision started from ~300 ka to 4300 ka. This is likely due to the covariation between the age of volcanism repaving and precipitation rates on Réunion, which is related to the configuration of the island’s two volcanoes – the active Piton de la Fournaise located on the windward side and the dormant Piton des Neiges on the center and leeward side. Our empirical calibration of the stream power law shows high dispersion in n and Kn on each individual island. m ranges from 0.2 to 2.9, and Kn ranges from 2.3 x 10-7 to 9.8 x 10-4 m1-2m/yr. For Réunion, we identify a positive trend between mean annual precipitation and erosion rates, and between mean annual precipitation and Kn, for low to moderate erosion rates (<1 mm/yr). For all basins of Réunion, there is also a positive trend between mean annual cyclonic precipitation rates and erosion rates, and between mean annual cyclonic precipitation rates and n. In Kaua’i, there is a positive trend between erosion rates and mean annual precipitation, consistent with previous studies. In Réunion, the proportionality coefficient between erosion and mean annual precipitation is three times greater than in Kaua’i. In addition, considering all three islands, a nonlinear relationship exists between channel slope and incision rate: best-fit n values range from 0.5 to 6, with n generally lower than one on Kaua’i. Our results highlight different sensitivities of fluvial relief to incision, and of incision to climate, between Kaua’i and Réunion islands.

 

How to cite: Gourbet, L., Gallen, S. F., Famin, V., Michon, L., Ramanitra, M. O., and Gayer, E.: River incision on hotspot volcanoes: insights from paleotopographic reconstructions and numerical modelling, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2631, https://doi.org/10.5194/egusphere-egu24-2631, 2024.

15:05–15:15
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EGU24-11817
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ECS
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On-site presentation
Sebastián Granados, Nicola Surian, and Guillermo E. Alvarado

 Active volcanic catchments within low-latitude tropical humid climates constitute some of the most dynamic and sediment-rich fluvial systems globally. The combination of factors such as active explosive vulcanism, frequent high-magnitude earthquakes, dense biodiverse vegetation, and intense rainfall leads to very high sediment supply and very active channel morphodynamics within such fluvial systems.

Our research focused on channel dynamics in three remote and challenging-to-access reaches of the Sucio River, situated within the Irazú stratovolcanic structure in Costa Rica's central volcanic chain. This unique setting experiences extreme conditions, including rainfall exceeding 8000 mm annually, infrequent but significant volcanic eruptions (occurring over three times per century), high-magnitude earthquakes (>Mw5), and dense pristine vegetation. The mapped river reaches within this active volcano exhibit a distinctive confined multi-thread channel morphology predominantly comprised of coarse sediments, notably boulders, displaying exceptional dynamism. These reaches showcase rapid shifts between braided, island-braided, and anabranching morphologies in relatively short periods (<20 yrs.). Additionally, the primary sediment sources located in crateric areas have undergone rapid and substantial changes, resulting in the emergence of large landslides and drastic alterations in vegetation.

Employing remote sensing techniques, geostatistical analysis, and fieldwork, we investigated the impacts of eruptions, earthquakes, and rainfall on the Sucio River's channel morphology and its primary sediment sources (craters) from 1961 to 2023. Over 65 images were processed to generate various derived raster products, including supervised classification datasets, change detection outputs, and morphometric parameters (such as channel width, braided index, anabranching index, and area of bars and islands). Moreover, we constructed a precipitation database spanning the study period to assess the frequency, magnitude, and duration of extreme rainfall events. Historical seismic data was utilized to compile a database of relevant earthquakes that might have affected the catchment, given the river's proximity to several active faults. Subsequently, exploratory statistical analysis employing linear regression models helped discern the influential factors behind channel dynamics and changes.

Our findings provide a novel understanding of how this specific fluvial volcanic environment responds to external perturbations and adapts its channel morphology over time. Key outcomes include the rarity of the multithread boulder morphologies observed in these reaches, rapid morphological transformations occurring within this multithread system in short intervals, the significant role of dense pristine vegetation in stabilizing banks and islands, and the cyclic stability-instability phases (erosion-deposition) triggered by pivotal events like eruptions, hurricanes, and high-magnitude earthquakes.

 

This study presents novel insights into channel morphology dynamics in one of Central America's most extensively studied active volcanoes, likely having the river transporting the most sediments in Costa Rica's volcanic regions.

How to cite: Granados, S., Surian, N., and Alvarado, G. E.: River dynamics in an active volcano with tropical humid conditions, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11817, https://doi.org/10.5194/egusphere-egu24-11817, 2024.

15:15–15:25
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EGU24-6783
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On-site presentation
Maria Cristina Zarazúa-Carbajal, Greg A. Valentine, and Servando De la Cruz-Reyna

A consequence of alluvial processes acting on scoria cones is the development of a drainage network composed of radially distributed rills and gullies parallel to the volcanic edifice's downslope direction. This work focuses on the quantification of the degree of development of the drainage network by applying the Average Erosion Index method to scoria cones from the arid to semi-arid Lunar Crater volcanic field and comparing with previously obtained results from two tropical volcanic fields (Sierra Chichinautzin volcanic field and Paricutin-Tancitaro region, both in central Mexico). The results show that the method helps to determine geomorphic age relations when calibrated separately for each field. Furthermore, the differences in the resultant rates at which AEI varies as a function of time obtained for the three studied fields indicate that the method provides a tool to quantify the effects of different alluvial rates at volcanic fields across various environments.

How to cite: Zarazúa-Carbajal, M. C., Valentine, G. A., and De la Cruz-Reyna, S.: Gully incision development on scoria cones: different behaviors in three volcanic fields reflect environmental conditions., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6783, https://doi.org/10.5194/egusphere-egu24-6783, 2024.

15:25–15:35
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EGU24-13012
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ECS
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On-site presentation
Roos M. J. van Wees, Engielle Paguican, Daniel O'Hara, Gabor Kereszturi, Pablo Grosse, Pierre Lahitte, and Matthieu Kervyn

Analogue experiments can enhance our understanding of complex natural volcanic landscapes formed by eruptions, intrusions, remobilisation of volcanic material and erosional processes. Experimental setup in a laboratory offers a controlled setting to investigate the development of rainfall-induced radial drainage basins on scaled volcano cones. It allows to simulate surface runoff, a prominent sediment transport process in volcanic landscapes, primarily influenced by climate, lithology, and topography. By controlling the flowrate within the setup, maintaining a uniform lithology, and using initial axisymmetric cones with the same size, this study aims to record the variations in erosion patterns caused by systematic cone slope and shape changes.

Analogue volcanic cones made up of water-saturated 70 μm silica powder were built upon a drainage layer of coarse sand at the VUB volcanology analogue laboratory. The cones were scaled based on the height/basal width ratios of natural pristine composite volcanoes with a scaling factor of 4.5*10-6 for the basal width. Initial cones had basal widths of 33 cm with two sets of cones with heights ranging from 4.2 to 6.9 cm. For the highest cones, the lower flank was 21 degrees and the upper slope 30 degrees, with a break-in-slope at 45% of the cone height. Experiments included cones with and without summit craters, the craters were 5 cm wide and 0.5 cm deep. Rainfall-induced erosion was simulated with two atomizer sprinklers, creating a mist of droplets of circa 30 μm. Experiments were run for 3 to 5 hours, simulating erosion taking place over several millions of years at natural volcanoes. We generated a minimum of ten Digital Elevation Models (DEMs) by photogrammetry with sub-millimetre spatial resolution, enabling the estimation of volume loss and erosion rates. The automated algorithms MorVolc and DrainageVolc were used to extract morphometric and drainage parameters (e.g., height/basal width ratio, drainage density, irregularity index) from the DEM of each timestep.

The analogue models' drainage networks and morphological characteristics replicate those found on natural volcanoes. Having a steeper slope for the upper flank of the cone delayed the forming of erosional features on the lower flank, while the top part of the volcano incised deeper than the cones with one slope gradient. The cones without a summit crater develop a radial drainage network from an initial set of narrow gullies to a more stable pattern with fewer valleys that gradually widen. The introduction of a summit crater substantially modifies the resulting erosional patterns: the incision of the crater rim forms two to four dominant watersheds that widen faster than the basins of cones lacking a crater. Migration of drainage divides ceases when equilibrium in the landscape is attained, with cones featuring a summit crater reaching this equilibrium later than those without. Analogue experiments are a valuable tool for studying erosional processes in a controlled manner and give insight into complex volcanic landscapes, thereby improving our understanding of long-term volcanic landscape evolution.

How to cite: van Wees, R. M. J., Paguican, E., O'Hara, D., Kereszturi, G., Grosse, P., Lahitte, P., and Kervyn, M.: Modelling volcano degradation through analogue experiments: the impact of volcano slopes and summit craters on erosion patterns, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13012, https://doi.org/10.5194/egusphere-egu24-13012, 2024.

15:35–15:45
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EGU24-11744
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Highlight
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On-site presentation
Dávid Karátson and Jean-Claude Thouret

We present a new book aimed at graduate students, and academics, as well as all volcano enthusiasts. We chose to publish on the topic of volcano geomorphology for two main reasons. Firstly, although several geomorphology textbooks have been published, ones focussed on volcano geomorphology are scarce or outdated and out of print (Cotton, 1944, McDonald, 1972; Ollier, 1969 and 1988). Secondly, many volcanology books have been published over the past few decades, but they do not describe landforms and geomorphic processes in sufficient detail (as stated by the late P. Francis in 1993). To our knowledge, only five modern books on volcanology include a chapter on volcanoes as landforms and landscapes (Francis, 1993 and Francis & Oppenheimer, 2004; Chester, 1993; Scarth, 1993; Lockwood and Hazlett, 2010). They are less process-oriented than modern books on geomorphology.

Our book on Volcano Geomorphology is organised into five main themes, and contains 10 chapters. The first theme is an overview of the geodynamic environments in which the Earth's volcanoes are createdThe second is a detailed account of elementary “constructional” landforms, from lava forms to monogenetic volcanoes, both terrestrial and subaqueous, reflecting a variable degree of magma-water interaction. The third deals with polygenetic volcanic edifices including shield volcanoes, composite cones and volcanic clusters. This is followed by landforms and processes that form calderas, caldera complexes, and volcano-tectonic depressions. The fourth is oriented towards the degradation of volcanoes by short- and long-term erosion processes. The fifth and final theme is twofold: first, we deal with geomorphic hazards on active and dormant volcanoes, along with five specific case studies of recent events; and lastly, we conclude with a chapter presenting a wide array of methods (morphometry, simulations of processes, structural geology, age determination, etc.) that are used to unravel processes on active and dormant volcanoes.
            In summary, our textbook aims to: (1) review the most recent research in geomorphology and physical volcanology, e.g. an improved classification and understanding of volcanic landforms, with respect to geodynamic settings, lithology, and climate; (2) update our knowledge of processes and rates of growth and destruction of volcanic landforms and landscapes by integrating recent results from the expanding sector of volcanology both in the field and in the laboratory; (3) consider how volcanic landforms, landscapes, and processes can be studied by reviewing classical and modern methods.  

In this way, we hope that our compilation, which provides a richly referenced and illustrated piece of work on volcano geomorphology, will be of interest to a broad audience. It is expected to be published later this year (2024).  

How to cite: Karátson, D. and Thouret, J.-C.: ‘Volcano Geomorphology: landforms, processes and hazards’  ̶̶ A new book in ‘Advances in Volcanology’ Collection, Springer Verlag , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11744, https://doi.org/10.5194/egusphere-egu24-11744, 2024.

Posters on site: Fri, 19 Apr, 10:45–12:30 | Hall X2

Display time: Fri, 19 Apr 08:30–Fri, 19 Apr 12:30
Chairpersons: Ingo L. Stotz, Paula Castillo, Matthieu Kervyn
X2.40
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EGU24-440
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ECS
Aisling Dunn, Nicky White, Robert Larter, Megan Holdt, Simon Stephenson, and Chia-Yu Tien

Accurately constraining past and future ice sheet evolution requires a quantitative understanding of key boundary conditions in ice sheet models, including topography and heat flux. Both of these conditions are in part moderated by spatially and temporally variable mantle dynamics. This study exploits an interdisciplinary approach to probe the mantle beneath Antarctica to better understand sub-crustal processes. First, observed bathymetry and topography are corrected for isostatic effects to isolate the residual topographic signal, a proxy for dynamic mantle support. In this way, a comprehensive suite of oceanic residual depth (n = 1120) and continental residual elevation (n = 237) spot measurements are calculated. Secondly, basaltic rare earth element concentrations acquired from an augmented database of Neogene volcanic samples (n = 264) are inversely modelled to determine melt fraction as a function of depth. Thus, we constrain mantle potential temperature and depth to the top of the melting column (i.e. lithospheric thickness). Finally, results from these approaches are interpreted alongside other geological and geophysical data, including free air gravity anomalies and mantle tomographic models to understand present day mantle-lithosphere interactions. Sequence stratigraphic analysis along continental margins (e.g. offshore from Dronning Maud Land and the Wilkes and Aurora Subglacial Basins) is also used to constrain temporal changes in mantle-induced vertical plate motion. Robust observations in the oceanic realm evidence dynamic support beneath the central Scotia Sea, the Marie Byrd Seamounts, in the vicinity of the Astrid Ridge, and beneath the Emerald Fracture Zone. Residual topography measurements define the extent to which these dynamic swells continue onto the continent, with 1-2 km of mantle support throughout West Antarctica, the Transantarctic Mountains, and the Gamburtsev Subglacial Mountains. Collectively, these results highlight considerable spatial and temporal variation in dynamic mantle support throughout Antarctica, making it imperative to account for such mantle-lithosphere interactions when modelling the onset and evolution of glaciation.

How to cite: Dunn, A., White, N., Larter, R., Holdt, M., Stephenson, S., and Tien, C.-Y.: Spatial and temporal variation in dynamic mantle support of the Antarctic plate: Implications for ice sheet evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-440, https://doi.org/10.5194/egusphere-egu24-440, 2024.

X2.41
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EGU24-17475
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ECS
Oliver Henke-Seemann and Lena Noack

Tectonic processes shape the Earth's lithosphere and surface. Deformation, as a result of tectonic forcings, arises mainly in the regions of plate boundaries. A recurring process is the subduction of oceanic lithosphere, which is widely regarded as the main driver of plate tectonics and the recycling of surface material into the mantle. In geodynamic models, the breaking of the strong crust is facilitated by processes that mimic plastic deformation. Most efforts to include plate tectonics self-consistently into mantle convection models, combine Newtonian diffusion creep with a stress-dependent pseudo-plastic rheology, given in the form of a yield criterion. Studies from seismology and geodynamic modelling indicate that cold lithospheric crust can reach the lowermost mantle regions, even the core-mantle-boundary. Additionally, the agglomeration of continental lithosphere (the most extreme variants of which are called supercontinents) inhibits the escape of heat over large surface areas, resulting in an abnormally heated mantle beneath. Therefore, it can be argued, that surface processes exert control on mantle dynamics as a whole, by introducing thermal and compositional heterogeneities.

An example of the influence of surface tectonics on the interior can be found in the study of the Earth's geodynamo. Theoretical considerations and numerical models indicate, that the heat flux at the core-mantle boundary partly governs the variability of the geodynamo, and therefore the frequency of geomagnetic reversals and excursions. 

We run several numerical mantle convection simulations in a 2D-spherical annulus geometry, with a visco-plastic rheology to facilitate surface mobilisation. The models are evaluated with respect to well-known diagnostic values, used to recognise plate-like surface deformation, as well as the thermal structure of the lower mantle. In this, we aim to connect tectonic regimes or continental configurations that arise dynamically at the surface, to evolutionary trends in the mantles thermal structure.

How to cite: Henke-Seemann, O. and Noack, L.: Surface regimes can provide an inherent perspective into interior dynamics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17475, https://doi.org/10.5194/egusphere-egu24-17475, 2024.

X2.42
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EGU24-8609
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ECS
Philippa Slay, Megan Holdt, and Nicky White

Earth’s topography is both isostatically and dynamically supported. Sub-crustal density anomalies, caused by convective mantle processes, generate transient vertical motion at Earth's surface, producing the dynamic component of topographic support. Residual depth measurements are a well-established proxy for quantifying dynamic topography on oceanic crust and provide an observation-led approach to probing mantle dynamics. A global database of residual depth anomalies compiled from seismic reflection profiles and wide-angle seismic experiments is augmented with results obtained from interpreting further seismic experiments in the oceans surrounding the African continent. Residual depth anomalies are calculated by isolating and removing isostatic signals arising from sediment loading and crustal heterogeneity. Following these corrections, observed water-loaded depth-to-basement is compared to that predicted by the plate cooling model, with deviation equal to the residual depth anomaly. Coverage surrounding the African continent is improved, particularly in the Gulf of Guinea and Mozambique Channel. Results are consistent with previous observations, showing dynamic support of ± 1 km out to and including spherical harmonic degree l = 40 (i.e. ~ 1000 km). Results are corroborated by independent geologic and geophysical markers of subsidence and uplift. For example, volcanism and slow shear-wave upper mantle velocity anomalies associated with the Cameroon Volcanic Line indicate dynamic support. Improving the spatial sampling of residual depth anomalies provides insight into the influence of convective circulation on Earth’s surface, culminating in a more robust database against which geodynamic models of mantle convection can be benchmarked.

How to cite: Slay, P., Holdt, M., and White, N.: Implications of dynamic topographic measurements along Africa’s passive margins, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8609, https://doi.org/10.5194/egusphere-egu24-8609, 2024.

X2.43
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EGU24-7187
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ECS
Youngjun Lee and Changyeol Lee

Various subduction zone characteristics, including the slab dip, plate velocity, seismicity, and back-arc stress regime, show the global asymmetry with respect to the subduction direction. In particular, the east-directed subducting slabs show shallow dips and slow convergences, contrast to the steep dips and fast convergences of the west-directed subducting slabs. To explain the global asymmetry, the westward lithospheric motion or the eastward mantle wind with respect to the underlying mantle and the overlying plate, respectively, have been proposed. However, the causative force for the lithospheric motion, the tidal force between the Earth and Moon, is only acceptable when the asthenospheric viscosity is dramatically low such as 1015 ~ 1016 Pa·s, which could not globally exist in the mantle. The causative force for the mantle wind has left unknown even though the impact of the mantle wind has been verified. Past studies have shown that slabs sinking into the lower mantle can cause global mantle flow. That is, the slabs sinking at the eastern and western trenches around the Pacific ocean can cause the global mantle flow above the low-viscosity liquid outer core, expressed as the mantle wind. Therefore, to verify whether the subducting slabs around the Pacific ocean cause the mantle wind, we conducted a series of 2-D numerical models using an annulus-shape model domain, which simplifies the subduction history in the paleo- and present-Pacific ocean. Along with an allowance of dynamic subduction, both the realistic mantle viscosity and the major phase transition in the mantle were considered. Results show that the global-scale mantle wind is spontaneously formed by the imbalance in lateral mantle stresses owing to the subducting slabs around the Pacific ocean when the slippery core-mantle boundary operates as a lubricant layer, and the direction and magnitude of the mantle wind are periodically changed every tens of million years. When he eastward mantle wind occurs, it induces the relative westward drift of the plate, and as a result, the westward plate velocity becomes greater than the eastward plate velocity with respect to the hotspot reference frame. Simultaneously, the mantle wind pushes the west-directed subducting slab toward the ocean, forming steep slab dips but does the east-directed subducting slab toward the arc, forming shallow slab dips, consistent with the present subduction asymmetry in the Pacific ocean. After that, the negative buoyancy of the shallow slab steepens the slab itself, changing the direction of mantle wind westward; the opponent slab dips and plate velocities occur in the subduction zones. This study reveals that the present subducting asymmetry is a snapshot expression of the evolving global mantle flow, formed by the subducting slabs.

How to cite: Lee, Y. and Lee, C.: Spontaneous Formation of Mantle Wind by Subduction and Its Impacts on Global Subduction Asymmetry, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7187, https://doi.org/10.5194/egusphere-egu24-7187, 2024.

X2.44
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EGU24-1686
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ECS
Rodrigo I. Cerri, Fabricio A. Caxito, Christopher Spencer, George L. Luvizotto, George W.C. Junior, Nayara M. Santos, and Lucas V. Warren

The ubiquity of detrital zircon in clastic sediments and their typical high U and low common Pb contents, resulting in relatively high precision U-Pb age determination, made zircon one of the primary minerals for provenance studies. Yet, its high closure temperature (>900oC), limited growth of new zircon under upper amphibolite-eclogite facies, inherited bias towards zircon-rich sources (e.g., felsic plutonic rocks), and the refractory behavior in sedimentary deposits rarely representing first-cycle sedimentation, can hamper the ability to detect some key tectonomagmatic events. In this sense, other mineral assemblages, like detrital rutile, that is formed in medium- to high-grade metapelite and metabasite mainly during high-pressure and low-temperature subduction metamorphism, can be used to provide a more complete record of orogenesis with polyphase evolution. Herein, we present U-Pb detrital rutile ages from the Cambrian-Ordovician Tacaratu Formation (lowermost unit of the late Jurassic to Cretaceous Tucano-Jatobá Basin, that directly overlies the Borborema Province in its southern region) to track the complete polyphase evolution of southern Borborema Province in the northeastern Brazil. The geodynamic evolution of this structural province is still a matter of debate, with interpretations varying from reworking of Paleoproterozoic continental crust with sedimentation and metamorphism in intracontinental setting, to oceanic closure during a complete Wilson Cycle with or without terrane accretion. Considering the southern Borborema Province Sergipano Belt, subduction started ca. 740 Ma ending with collisional processes (ca. 590-570 Ma) associated with the closure of the Sergipano-Oubanguides oceanic basin. The Neoproterozoic Pernambuco-Alagoas Domain and Sergipano Belt, both formed due to the collision between São Francisco-Congo Craton and the Pernambuco-Alagoas superterrane, are the main source of detritus of the Tacaratu Formation. Coupled U-Pb detrital zircon and rutile analysis revealed that detrital zircon ages lags (i.e., are younger) detrital rutile ages by around 100 Ma. Detrital rutile and zircon present main young peaks at ca. 650 Ma and 545 Ma, respectively. Recently, Neoproterozoic arc-back-arc amphibolite (ca. 743 ± 3 Ma), a rare setting for the early phases of Brasiliano Orogeny, and Cordilleran-type medium- to high-K granites (ca. 645-610 Ma), were recognized in southern Borborema Province, in agreement with our detrital rutile U-Pb ages. Thus, our detrital rutile ages record earlier phases of Brasiliano Orogeny in the southern Borborema Province (subduction-related metamorphism; closure of Sergipano-Oubanguides ocean), since the Brasiliano Orogeny culminated in the collision of blocks that were followed by high-temperature metamorphism (hampering the formation of younger rutile?). Notwithstanding, detrital rutile ages interesting marks around late Tonian to Cryogenian subduction-related metamorphism, perhaps in a magma-poor orogenic phase.

How to cite: Cerri, R. I., Caxito, F. A., Spencer, C., Luvizotto, G. L., Junior, G. W. C., Santos, N. M., and Warren, L. V.: Detecting subduction-related metamorphic events during the early Brasiliano Orogeny in southern Borborema Province using detrital rutile , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1686, https://doi.org/10.5194/egusphere-egu24-1686, 2024.

X2.45
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EGU24-22053
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ECS
Revisiting tectonic models for the evolution of the Ellsworth Mountains in Antarctica: A key component for understanding the African-Antarctic section of the paleo-Pacific margin
Paula Castillo, Fernando Poblete, Rodrigo Fernández, Joaquín Bastias-Silva, C. Mark Fanning, Teal Riley, Jaime Cataldo Bacho, Ellen Rosemann, Cristóbal Ramírez de Arellano, and Katja Deckart
X2.46
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EGU24-3473
Alessandro Fornaciai, Massimiliano Favalli, Luca Nannipieri, Agnese Turchi, Rosanna Bonasia, and Federico Di Traglia

The Island of Vulcano is the emerged portion of a composite volcanic edifice within the Aeolian volcanic archipelago, situated in the southern Tyrrhenian Sea. The remobilization, triggered by heavy rainfall, of loose volcaniclastic material from La Fossa cone and the generation of small debris flows are recurrent hazards on Vulcano. Although these debris flows generally transport small volumes of material, in the case of severe events, they can  be channeled along the roads, flood several buildings, inundate the main harbor, and eventually be discharged into the sea. Gravitational and erosive processes, mainly due to rainfall, have formed several gully systems around the La Fossa cone. The presence of gully systems along slopes enhances both runoff and downslope mass wasting, and, above all, the gullies themselves act as a source of mass wasting due to the collapse of their walls and the processes of aggradation and degradation of their beds. Therefore, understanding the behaviour of gullies and their response to rainfall is crucial for predicting the effects of environmental changes, whether climatic or volcanic, on gully dynamics. 

In the frame of "VOlcaniclastic debris flows at La Fossa cone (Volcano  Island): evolution and hazard implication (VOLF)" project funded by the Istituto Nazionale di Geofisica e Vulcanologia, we here analyze aerial photos of the NW sector of La Fossa cone to describe the evolution of its gully system from the 1954 to 2022. First, we create a georeferenced dataset of photos by orthorectifying existing photos and generating new ones through the Structure from Motion (SfM) method applied to Unmanned Aerial System (UAS) photos. Second, we describe the geomorphological features of the gullies in the NW sector of La Fossa cone, identifying features to be parameterized. Finally, we qualitatively and quantitatively describe their evolution over almost 70 years.  

This work aims to investigate the morphological evolution of the NW flanks of La Fossa cone, a crucial aspect for assessing hazards associated with volcaniclastic sediment-charged flows and floods on Vulcano Island. This is especially relevant in a scenario where ongoing climate changes may potentially disturb the current equilibrium, heightening the likelihood of short-term extreme rainfall events.

How to cite: Fornaciai, A., Favalli, M., Nannipieri, L., Turchi, A., Bonasia, R., and Di Traglia, F.: The gully system on the NW sector of La Fossa cone (Vulcano Island): 2D evolution and hazard implication, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3473, https://doi.org/10.5194/egusphere-egu24-3473, 2024.

X2.47
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EGU24-15103
Daniel O'Hara, Liran Goren, Benjamin Campforts, Roos van Wees, María Cristina Zarazúa-Carbajal, and Matthieu Kervyn

Volcanic edifices are dynamic landforms whose morphology encodes the long-term (thousands to millions of years) interplay between construction and erosion. Short-term, stochastic episodes of volcanic activity cumulatively build topography, competing with stochastic erosive processes associated with climate and mass wasting to degrade edifices over longer timescales, thus generating a variety of morphologies from simple, cone-like edifices to complex, non-axisymmetric volcanoes. Understanding how these processes interact to shape volcano morphologies over the landform’s lifespan is still in its infancy, especially as construction and erosion are often spatially-heterogeneous and temporally-varying. Despite this, disentangling edifice morphologic histories provide new avenues to better discern an edifice’s volcanic record, assess potential hazards, and quantify the role of climate in landscape evolution.

Numerical modeling has been shown to be a useful approach to exploring long-term landscape evolution. Although the majority of studies have applied landscape evolution models to tectonic settings, modeling has also been applied to simulate erosion and drainage development for specific volcanic features (e.g., channel incision on shield volcanoes, soil diffusion on cinder cones). However, thus far no modeling frameworks have been developed to explore evolution over the full spectrum of edifice types

Here, we investigate volcanic edifice erosion and drainage basin formation using a simplified landscape evolution model. Assuming that the various erosive processes that shape a volcano can be simplified to the competition between advection and diffusion, we use common transport laws (stream power law and linear soil diffusion) to conduct a nondimensional parameter analysis. We then test various parameter combinations to demonstrate the range of morphologic evolutions that can occur over different edifice classifications and environments. Afterwards, we compare our results to previously-derived relationships of natural volcano evolutions to test the ability for simplified models to recreate nature. Finally, we explore the effects of edifice size on the competition between incision- and diffusion-based erosion within the framework of our nondimensional parameters by quantifying drainage development of 156 cinder cones from the Springerville Volcanic Field (AZ, U.S.) and comparing these to both edifice age and planform area.

Our results demonstrate that simplified numerical models are able to recreate the trends observed in nature. Furthermore, we show that the combination of model parameters predicts threshold sizes that volcanic edifices must overcome to begin generating fluvial drainage networks and becoming incised by gullies, broadly inferring parametric thresholds that describe the ratios of erosion processes on these landforms. Our results thus establish a new foundation to study edifice morphologies over several volcano types (cinder cones, shield volcanoes, composite volcanoes) and construction styles (intrusion-driven surface uplift, mantling by lava flows and ash deposits), and provides a basis to test how volcanic environments respond to past and future changes in climate and tectonics.

How to cite: O'Hara, D., Goren, L., Campforts, B., van Wees, R., Zarazúa-Carbajal, M. C., and Kervyn, M.: Understanding volcanic edifice erosion and morphologic evolution using numerical models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15103, https://doi.org/10.5194/egusphere-egu24-15103, 2024.

X2.48
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EGU24-15687
Matthieu Kervyn, Roos M.J. van Wees, Pablo Grosse, Pierre Lahitte, and Daniel O'hara

Volcanoes display a wide range of morphologies, resulting from the cumulative imprints of deposition from multiple eruptive events and processes, deformation by intrusive and gravitational processes, as well as erosion throughout the active volcanic phase and beyond. Quantitative documentation of the morphometry of volcanoes offers opportunities to compare volcanic edifices across tectonic regions, define evolutionary trends for volcanoes of different ages and/or stage, or compare natural volcanoes with results from analogue or numerical modelling. Although such morphometric studies exist, the comparability of their results faces challenges related to the contrasted approaches used for delineating volcanic edifices, defining morphometric metrics to characterize volcano sizes, shapes, and erosion patterns, and deriving the pre-erosional volcano volume.

Building upon the MORVOLC (Grosse et al. 2012) and ShapeVolc (Lahitte et al. 2012) algorithms, the EVoLvE project has produced a suite of scripts in MatLab to semi-automatically document the morphometry of stratovolcanoes systematically. First, the manual delineation of a volcano’s base is aided by implementing a slope threshold (suggested to be at 3°) after applying a 300m low-pass filter on the volcano’s topography to identify the prominent volcano landform. Morphometric parameters documenting volcano-scale size, plan-shape, profile shape and slope, as well as metrics derived at regular elevation intervals, following the MORVOLC approach of Grosse et al. (2012), are complemented with a new set of parameters (DrainageVolc) that document the erosion pattern of volcanoes, specifically the drainage density and the geometry of drainage basins. Finally, assuming basins’ divides or local quasi planar surfaces represent the least eroded sections of an edifice, a surface fitting algorithm (ShapeVolc, Lahitte et al. 2012) is used to find the best approximate pre-erosional shape of the volcano,  making it possible to compute its erupted and eroded volumes, and dismantling and degradation rates.

In this contribution, we illustrate how the EVoLvE toolkit can be used to systematically document the morphometry of stratovolcanoes across volcanic arcs, and with contrasted ages to highlight morphological evolution through time. The toolkit can as well be used to compare the morphometry of natural volcanoes with those of synthetic volcanic cones whose erosion is simulated through analogue experiments and numerical landscape evolution models. The Matlab codes of the EVoLvE toolkit are open-source: they aim to contribute to homogenizing the morphometric datasets for volcanoes around the world as a first step towards a more comprehensive understanding of the morphological evolution of volcanoes.

 

References:

Grosse, P., van Wyk de Vries, B., Euillades, P. A., Kervyn, M. & Petrinovic, I. A. 2012: Systematic morphometric characterization of volcanic edifices using digital elevation models. Geomorphology 136, 114-131.

Lahitte, P., Samper, A. & Quidelleur, X. 2012: DEM-based reconstruction of southern Basse-Terre volcanoes (Guadeloupe archipelago, FWI): Contribution to the Lesser Antilles Arc construction rates and magma production. Geomorphology, 136, 148-164.

How to cite: Kervyn, M., van Wees, R. M. J., Grosse, P., Lahitte, P., and O'hara, D.: The EVoLvE toolkit: a set of methods for systematic quantification of volcano morphometry and their temporal evolution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15687, https://doi.org/10.5194/egusphere-egu24-15687, 2024.

X2.49
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EGU24-15825
Pierre Lahitte, Louise Bergerot, Pablo Grosse, Roos M. J. van Wees, Daniel O’Hara, and Matthieu Kervyn

Understanding the temporal variations in erosion dynamics is crucial when exploring the intricate relationship between climates and the evolution of landforms. Volcanic surfaces constitute an undeniable asset for documenting temporal variations in erosion dynamics, as they readily reveal the onset of erosion. Indeed, the dating of volcanic materials constrains the age of eruptive activity, volcanic surface formation, and the time since erosion occurred. This study quantifies the Neogene and Quaternary erosional processes that shaped the current Lesser Antilles's volcanic reliefs. We apply morphometric approaches on high-resolution digital topographies of very densely dated volcanoes to discern the influence of factors driving erosion, focusing on climatic context and erosion duration.

The detailed analysis of the erosion signature's evolution was carried out on the French volcanic oceanic arc islands of Basse-Terre (Guadeloupe) and Martinique, thanks to the large number of geochronological constraints (around 100 K-Ar datings on each of them) and the high-resolution topography (LIDAR DEM at horizontal 1m resolution). The meticulous examination of erosion signatures is facilitated because magmatic activity, which produced the same kind of volcanic edifices in both islands, has undergone a spatial migration (westward in Martinique, southward in Basse-Terre). It results in outcrops of terrains spanning vastly different ages (0-3 and 0-25 Ma, respectively), providing a unique opportunity to investigate the distinct influences of geological processes on erosion signature. The study focuses on quantitative analysis of river-long profiles by scaling river profile concavity, hypsometric indexes and knickpoints, which are noticeable slope breaks or abrupt changes in the gradient of the river channel. Thanks to the dense geochronological database, metrics computed for each geomorphological feature can be associated with the age of formation of the local volcanic surface. Then, as these ages are relevant to the cumulated erosion process occurring since the end of the volcanic activity, such metrics can be correlated to the time and evolution trends in morphometric parameters can be investigated.

The 25 Ma-long erosion history of Martinique Island reveals two distinct patterns. During the initial 5 million years of erosion, there is a rapid increase in river concavities and a decrease in the intensity and number of heterogeneities along river profiles, resulting in smoother stream patterns. In contrast, over the 5-25 Ma erosion period, every river's morphometric parameters evolve slowly, suggesting a preservation of river concavity. This transition phase in concavity evolution could mark the moment when the rivers’ incision, driven by regressive erosion and carving into the volcano from every side, having finally affected the summit area, also reached a maximum concavity. Erosive processes then reduced the volcano's elevation but maintained a relatively uniform profile shape and, consequently, concavity over time. Despite Basse-Terre Island's shorter erosion history of 3 million years, morphometric parameters testify that this island experienced strictly similar evolution as Martinique Island during the same erosion lifespan, suggesting a comparable evolution of the Basse-Terre reliefs in the future.

How to cite: Lahitte, P., Bergerot, L., Grosse, P., van Wees, R. M. J., O’Hara, D., and Kervyn, M.: Dynamism of the Neogene and Quaternary erosional processes in the Lesser Antilles volcanoes, constrained by morphometric approaches, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15825, https://doi.org/10.5194/egusphere-egu24-15825, 2024.

X2.50
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EGU24-18291
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ECS
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Thomas Lemaire, Daniele Morgavi, Paola Petrosino, Sonia Calvari, Leopoldo Repola, Lorenzo Esposito, Diego Di Martire, and Vincenzo Morra

Lava tubes are an important transport mechanism in active lava flows. Their presence in a lava flow can influence its distance of emplacement due to the insulation of the hot molten lava by a cooled overlying crust. Understanding mechanisms of formation and development of lava tubes is fundamental to comprehend lava flow propagation and improve knowledge to better manage the hazard during a volcanic crisis. Vesuvius is known for its major explosive eruptions; however, in its history it underwent extensive periods of open conduit, with prolonged explosive activity and lava flows. After the 1631 eruption, Vesuvius entered an effusive period that ended with the 1944 eruption. During these 313 years, over one hundred lava flows emplaced on Vesuvius flanks, particularly the 1858 eruption which produced a compound pahoehoe lava flow that emplaced on the western flank of Vesuvius. 

In this study, we conducted: (1) a temporal and spatial reconstruction of the 1858 lava flow using historical documents (geological maps, paintings, descriptions of eruptions), (2) a morphological and surficial analysis of the 1858 lava flow as well as the definition of new contours based on geological maps and digital elevation models and (3) a complete morphological analysis of the lava tube using high-end technologies (time-of-flight terrestrial laser scanner, Lidar equipped drone and optical cameras).  

On the 1858 lava flow field surface we found numerous tumuli and ephemeral vents. We discovered a small lava tube present in a flat area of the lava flow field (<3°) with ropy to slabby pahoehoe surface lavas. The lava tube is oriented north-south, perpendicular to the main flow direction. It is triangularly shaped with a length of 30.05 meters and a width that varies from 1.20 to 17.61 meters from the northern to the southern part. The average height is around 2 meters. The slope along the flow direction is on average 4.48°. We measured a mean roof thickness of 2.4 meters. The roof is fractured and has collapsed in different areas of the lava tube. Inside, we observed features that relate to the temporal evolution of the lava tube. Stalactites are present on the ceiling of the tube suggesting a prolonged flow of lava within the tube. Multiple layers of lava are covering the wall of the lava tube, the last wall lining is five to seven centimeters thick and, in some areas of the lava tube, has detached from the wall and rolled down on itself, testifying to a sudden drainage of the lava tube when the lining was still plastic.  

The results of the study of the 1858 lava flow field and of its lava tube are essential for expanding our knowledge about the processes at the basis of lava flow field emplacement and development on Vesuvius and the first attempt focused on understanding effusive dynamics governed by lava tube formation (i.e., lava emplacement) at Vesuvius.

How to cite: Lemaire, T., Morgavi, D., Petrosino, P., Calvari, S., Repola, L., Esposito, L., Di Martire, D., and Morra, V.: Lava tubes formation and extensive flow field development during the 1858 eruption of Mount Vesuvius. , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18291, https://doi.org/10.5194/egusphere-egu24-18291, 2024.

X2.51
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EGU24-20357
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ECS
Tamás Biró, Pierre Lahitte, Maxim Portnyagin, Emő Márton, Emőke Mohr, Márton Palotai, Sándor Józsa, Levente Iván, Márton Krasznai, Mátyás Hencz, Jean-Louis Paquette, János Hír, Fanni Vörös, and Dávid Karátson

Silicic ignimbrite volcanism played a major role in the Miocene evolution of the Central Paratethys. The most voluminuous ignimbrites identified to date (18.1–14.4 Ma) were emplaced in various paleoenvironments in the North Pannonian Basin, thus they are extremely helpful in regional stratigraphy. Here, we present the discovery of a previously unknown but widespread, youngest member of the “Upper Rhyolite Tuff“, referred to as Dobi Ignimbrite, which shows a distinctive glass geochemistry. High-precision sanidine and plagioclase Ar-Ar dating yielded 13.066±0.019 Ma (earliest Sarmatian stage in Paratethys chronology), significantly shifting the previously claimed termination (i.e. Badenian) of the North Pannonian ignimbrite flare-up. In addition, we demonstrate that, although the Dobi Ignimbrite is underlain by a marine sedimentary succession, it was emplaced on land, as it bears leaves and tree trunk fragments and is rich in charcoal. Despite the highly faulted terrain as well as intense dissection and erosion controlled by the neotectonic evolution of the Pannonian Basin, the observed areal extent (c. 1000 km2) and calculated minimum volume (c. 50 km3) of the ignimbrite may represent a VEI= 6 or 7 eruption, which needs to be further delineated. At the same time, the ignimbrite has a strongly phreatomagmatic character, suggesting an abundant, possibly shallow sea- or residual lake water source that was likely limited to the vent area (e.g. caldera graben). The detected sharp environmental change from submarine to terrestrial, as defined by the timing of ignimbrite emplacement at c. 13 Ma, marks the latest Badenian regressive period, followed by a Sarmatian erosion during the Central Paratethethys evolution.

 

How to cite: Biró, T., Lahitte, P., Portnyagin, M., Márton, E., Mohr, E., Palotai, M., Józsa, S., Iván, L., Krasznai, M., Hencz, M., Paquette, J.-L., Hír, J., Vörös, F., and Karátson, D.: A newly discovered youngermost (13.07 Ma) “Upper Tuff”, a large-volume phreatomagmatic ignimbrite in the Pannonian Basin, drapes the present, faulted/dissected topography , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20357, https://doi.org/10.5194/egusphere-egu24-20357, 2024.

X2.52
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EGU24-20487
Hugo Delgado Granados and Daniela Hernández Villamizar

Four monogenetic volcanoes were formed during the last 100 ka (Late Pleistocene), west of the city of Morelia (Mexico), in the central-eastern part of the Michoacán-Guanajuato Volcanic Field, located in the central region of the Trans-Mexican Volcanic Belt. These include four scoria cones (Melón, Mina, Tzinzimacato Grande, and Tzinzimacato Chico) and some lava flow deposits associated with the material emitted during the effusive phase of the volcanoes. From the study of stratigraphic relationships in the field and geological mapping, the eruptive chronology of the monogenetic volcanoes was determined. Subsequently, based on the analysis of the morphological (flow dimensions) and petrographic characteristics, the eruptive parameters (effusion rate and emplacement time) and the rheology of the lavas were estimated. The flow units of the effusive phase of the volcanoes present different morphological and mineralogical characteristics. The flows with greater slopes have average viscosities of 2.7x108 P and a higher volume content of phenocrysts; the value of this property decreases in the flows with lower slopes, 1.7x108 P as respectively. The results indicate that the most voluminous eruption corresponds to that emitted by the Mina volcano, with an effusion rate of 2.3 m3/s and a total duration of 239 days. The Tzinzimacato Chico volcano emitted a smaller volume of lava during its eruption, with an effusion rate of 0.9 m3/s and a total duration of 117 days, which is considered the most recent.

How to cite: Delgado Granados, H. and Hernández Villamizar, D.: Eruptive parameters of volcanoes Melón, Mina, Tzinzimacato Grande, Tzinzimacato Chico (Mexico) from morphology and petrographic studies , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20487, https://doi.org/10.5194/egusphere-egu24-20487, 2024.

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EGU24-21095
Lucía Sáez-Gabarrón, David Sanz-Mangas, Inés Galindo-Jiménez, Juana Vegas, Juan Carlos García-Davalillo, Mario Hernández, Raúl Pérez-López, Carlos Camuñas, Gonzalo Lozano, Carlos Lorenzo Carnicero, Miguel Ángel Rodríguez-Pascua, Maria Ángeles Perucha, Julio López Gutiérrez, and Nieves Sánchez

During the 2021 eruption on La Palma Island, the predominant volcanic hazard was lava flows, while tephra fall and gas emission were significant concerns. Consequently, monitoring the expansion of the lava flow perimeter considering the variations in volcanic activity became fundamental. The interaction of lava with the sea water was also a major concern for emergency managers due to its associated hazards like gas emission and explosive activity due to interaction lava-water, leading to a specific focus on the formation and development of lava deltas.

Almost 10 days after the beginning of the eruption, the lava reached the sea, forming a main structure (south delta) that grew in different phases until nearly the end of the eruption, covering an area of approximately 83 ha. The south delta encroached upon the sea and additionally buried the northern part of a pre-existing lava delta from the 1949 San Juan eruption. About 1300 m from the northernmost tip of the south delta, a new lava flow entry to the sea occurred 64 days into the eruption, feeding a second lava delta (north delta) of about 5 ha over a 4-day period.

This study has made significant technical and scientific contributions, not only during the emergency but also in preparation for future recovery efforts on La Palma. Remotely Pilot Aircrafts (RPAs) provided valuable information about the lava-flow development and enhanced a deeper understanding of the formation and evolution of lava deltas and their potential hazards. Moreover, the study highlights the potential impact on new inhabited or economically exploited areas and is imperative its preservation for the geological heritage, including marine zones. Furthermore, it will play a crucial role in forecasting the behaviour of lava deltas and in the development of mitigation measures for potential future eruptions.

How to cite: Sáez-Gabarrón, L., Sanz-Mangas, D., Galindo-Jiménez, I., Vegas, J., García-Davalillo, J. C., Hernández, M., Pérez-López, R., Camuñas, C., Lozano, G., Lorenzo Carnicero, C., Rodríguez-Pascua, M. Á., Perucha, M. Á., López Gutiérrez, J., and Sánchez, N.: Evolution and Growth of Lava Deltas: Insights from the 2021 La Palma Eruption (Canary Islands), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-21095, https://doi.org/10.5194/egusphere-egu24-21095, 2024.

Posters virtual: Fri, 19 Apr, 14:00–15:45 | vHall X2

Display time: Fri, 19 Apr 08:30–Fri, 19 Apr 18:00
Chairpersons: Ingo L. Stotz, Paula Castillo, Matthieu Kervyn
vX2.4
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EGU24-8475
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ECS
Margherita Scala, Maria C Neves, and Stéphanie Dumont

Understanding the relationships between the onset of volcanic eruptions and external forcings, such as solid Earth and ocean tides, can help us to understand the underlying dynamics of volcanic processes and have implications for volcanic monitoring and prediction efforts.

Many studies that explored the relationship between tidal forces and volcanic activity have shown that certain phases of tidal cycles are associated with an increased likelihood of eruptions. At longer-time scales of hundreds of thousands of years, pronounced sea level variations related to ice melting or climatic and astronomical periodic variations have also been associated with pulses of volcanic activity.

Oceans participate in significant redistributions of mass that can affect the stress field within the Earth’s crust over different time scales. Considering that most volcanoes lie near, within or beneath the oceans we hypothesize that stresses induced by ocean loading participate in destabilizing volcanic dynamical systems and ultimately contribute to eruption triggering.

In a previous study we analyzed the worldwide number of monthly volcanic eruptions from the Global Volcanism Program and the global mean sea level between 1880 and 2009 using the Singular Spectrum Analysis time-series analysis technique. We found common periodicities and particularly multi-decadal components of similar periodicities of 20, 30 and 50 years present in both time-series.

In this work we further explore the connection between volcanic activity and sea level by mapping the spatial patterns of volcanic eruptions at the previously identified temporal scales of correlation, ranging from the fortnightly tide to cycles of approximately 100 years. Geographical Information System tools are used to create spatial data layers, perform spatial analysis, and provide geographical visualization. The analysis might reveal global conditions and space-time patterns favorable to eruption triggering.

This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) –

UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020),

UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and

LA/P/0068/2020(https://doi.org/10.54499/LA/P/0068/2020).

How to cite: Scala, M., Neves, M. C., and Dumont, S.: Patterns of volcanic eruptions in connection to sea-level change, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8475, https://doi.org/10.5194/egusphere-egu24-8475, 2024.